Climate and Global Warming Issues and Uncertaines (Don Bogard) USofA

CLIMATE & GLOBAL WARMING ISSUES: UNCERTAINTIES IN ITS CAUSE, ITS EXTENT, AND WHAT CAN BE DONE ABOUT IT My Personal Perspective: Donald Bogard, May, 2017

Colorado Rocky Mountain Springtime

"The overview consideration presented here introduces many diverse topics, all relevant to future temperature changes, but none is covered in detail. My purpose here is to raise several “issues" about climate, but not to give an answer. Rather, I emphasize the breadth and complexity of the subject and briefly present some of the considerable issues and uncertainties in various parameters."

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What is the Issue?

When we consider ongoing and future climate change, uncertainties abound.

Since the late 19th century, Earth’s average global temperature has apparently increased by about 0.8 degree Celsius (deg-C). Many attribute this entire warming to increasing atmospheric CO2 due to human activities, whereas others attribute only part or none of the recent warming to CO2 and attribute the rest to other causes. (A few deny there has been any warming.) Some fear future warming will bring climate catastrophes, and they advocate rapid and drastic changes in human activities, especially in methods of energy generation and use. However, others argue that both the uncertainties over future warming and over various solutions proposed to counter effects of warming are too poorly understood to undertake drastic action, and that rash actions may produce more harm than good. Further, even if future warming is anticipated, whether caused by greenhouse gases or not, it is not obvious what could or should be done about it.

The overview consideration presented here introduces many diverse topics, all relevant to future temperature changes, but none is covered in detail. My purpose here is to raise several “issues” about climate, but not to give an answer. Rather, I emphasize the breadth and complexity of the subject and briefly present some of the considerable issues and uncertainties in various parameters.

The underlying question is this. Given uncertainties in various climate parameters and in possible mitigation activities for global warming, how reliably can future outcomes be predicted? The intended audience is those who may know little about details of climate change, but who

are interested broadly in issues associated with global warming, its risks, and proposed attempts to control it.

In raising these issues, I am not being a climate change denier, as climate frequently changes. I am not even a global warming skeptic, for I accept that the Earth is slowly warming. What I do question is how well we know how much it is warming, what are the various reasons, and what, if anything, can and should be done about that. The extreme polarization of viewpoints that has arisen over the subject does not readily provide the correct answers or elucidate what actions should be taken. If you give a person facts, you give him knowledge. If you teach a person to think, you give him wisdom.

The broad climate topic requires wisdom.

Temperature Measurements There is no doubting that Earth’s temperature varies. Temperature changes considerably between day and night and with seasons of the year, and it has varied over geologic time. At any given time the surface temperatures at points around the Earth are very different. So, how is Earth’s average global temperature determined at any specific time and how accurate is it? There are four basic readings of Earth temperatures – the atmosphere, the land surface, the oceans, and infra-red heat escaping into space.

Atmospheric temperature in the troposphere is determined by microwave sounding from satellites looking down, 2

which cover a large fraction of Earth’s surface at frequent intervals. Troposphere temperature is also determined by balloons making direct temperature measurements, and these usually are in good agreement with satellite measurements. These atmospheric measurements are generally considered the most accurate. However, Earth’s atmosphere contains very little of Earth’s surface heat, less than 0.1%, and energy is constantly being exchanged among different heat reservoirs (especially by water evaporation and precipitation). So, an important question is how accurately such atmospheric temperatures reflect change in Earth’s total energy content.

The fraction of Earth’s near-surface energy contained within the land surface is several percent of the total and is measured daily by over 1,000 temperature-reporting stations distributed around the world. (Measurements are actually made of the atmosphere 1.5 meters above the land surface, where temperature is dominated by the land temperature beneath.) However, these temperature stations are not evenly distributed; e.g., the US and other developed countries have many, whereas high latitude regions and unpopulated areas have few. Further, some stations are not well maintained, and their temperature readings are often suspect. It has been well documented that many older stations are now located in urban areas, at airports, near parking lots, and other places where local temperatures are often artificially increased. Recorded temperature over land in the US has largely increased at night and at higher latitudes. The U.S. Climate Reference Network of over 100 “superior” temperature measuring stations was established in 2005. Both the maximum

and minimum average temperatures from these stations show yearly variations, but no obvious trend over time.

The oceans hold the large majority of Earth’s surface heat. However, their past temperature has been poorly measured, primarily measured near the ocean surface, and only recently have there been deployed quality measuring devices (e.g., buoys and ARGO floats). These remain too few to fully measure ocean temperature across the globe and at all ocean depths. Plus, because of the tremendous heat capacity of oceans, changes in ocean temperature produced by overall global warming is expected to be very small, a fraction of one degree.

Ocean temperature varies considerably in different locations and depths, and changes are difficult to measure accurately and must account for variable mixing among various ocean layers. On average, ocean temperature changes suggest some warming. To complicate the situation further, some researchers modify individual land and sea temperature measurements considered “suspicious”, using procedures that themselves may not be optimal. Temperatures for large areas of the world without reporting stations are “assumed” by utilizing surrounding measured temperatures. Further, neither the specific land and ocean stations nor the method of making temperature measurements have remained constant over extended time. Recorded night-time land temperatures have increased considerably more than daytime temperatures.

Since 2001, NASA’s CERES program (Clouds and the Earth’s Radiant Energy System) has measured the change in energy escaping from the Earth into space.

[CERES monitors the average rate of escaping infra-red energy, the sole means 3

by which Earth loses heat. Temperature is not directly measured. Any change in this rate of heat escape over time could indicate that Earth is warming.] CERES data indicate that Earth has been gaining energy at an average rate of 0.7 watts per square-meter of surface area (with a yearly variation of 0.3-1.4 w/m2). The CERES data are considerably more precise than ocean temperature measurements. In contrast, atmospheric temperatures reveal little to no significant warming over the past two decades. Clearly better understanding of how Earth transfers heat among its different reservoirs is required to interpret these differences.

Whatever the uncertainties in various individual temperature measurements, all these are combined to produce average global temperature. The indication is that over the past century global temperature has increased by about 0.8 degree-C. Only part of this increase occurred since human CO2 emissions began to strongly increase about 1950. How reliably the increase in global temperature has been recorded may be a matter of some conjecture, although the evidence is strong that the Earth has slightly warmed. The exact amount of warming and when are important, because the validity of climate models predicting future temperature trends depend on them.

throughout the atmosphere but varies seasonally on a regional level, has been steadily increasing for some hundred and fifty years and is now around 405 parts per million (ppm, or 0.04%).

Atmospheric CO2 has been continuously monitored since 1959, and various intermittent measurements exist prior to that. Over more recent geologic time (last 500 million years), atmospheric CO2 was widely variable and ranged from a low of about 180 ppm (during limited past periods of intense glaciation) to several thousand ppm. Our current 405 ppm ranks relatively low compared to most past CO2 levels.

Human activity accounts for most atmospheric CO2 growth over the past century. Over much of the past century good records have been kept of the amount of fossil fuels extracted and burned. In addition, land use practices (e.g., burning forests, planting crops, husbandry) and other activities (e.g., cement making and metal smelting) also contribute. CO2 produced by that fossil fuel burning considerably exceeds the growth of atmospheric CO2. About half of the CO2 humans have contributed to the atmosphere has been removed via dissolution into the oceans and by plant photosynthesis, where CO2 has prompted increased plant growth. Natural processes affecting the atmospheric CO2 abundance include addition by volcanoes and rock weathering and removal in the oceans by organisms forming carbonate shells and subsequent precipitation as limestone.

These natural processes are slow compared to recent rates of CO2 production by human activities.

CO2.

Atmospheric CO2 concentration, which is reasonably well-mixed

Greenhouse Gases.

The most important greenhouse gas by far is atmospheric water vapor, and it 4

accounts for the great majority of greenhouse warming of the Earth. Water vapor in Earth’s atmosphere can vary from almost none to a few percent. Water enters the atmosphere by evaporation from the surface (especially oceans), returns to the surface via rain or snow, and often forms clouds (aerosols of tiny liquid drops). Thus, the abundance of water vapor in the atmosphere and the degree of greenhouse warming it produces is highly variable across the Earth’s surface and over time. Clouds can act both to reflect some solar radiation back to space and to slow infra-red radiation in escaping from Earth’s surface into space.

Which effect is dominant over space and time frequently is not obvious. This variability of atmospheric water, in its various forms, is perhaps the greatest uncertainty about future greenhouse warming.

CO2 is the second most important greenhouse gas, and like all greenhouse gases it can slow heat escape from the Earth and thereby increase global temperature. [The Earth receives virtually all its energy from solar radiation and loses all of it by infrared radiation (IR) from the high atmosphere to space. Greenhouse warming is achieved through greenhouse gas absorption of IR as it is radiated from Earth’s surface. This IR experiences multiple absorption and radiation processes as the energy moves toward the upper atmosphere and eventually escapes. A simple analogy to the process would be like donning an overcoat on a cold day, thereby trapping more of the body’s heat inside. But greenhouse warming is more complicated.]

Without these greenhouse gases, the Earth likely would be about 33 deg-C (59 degrees Fahrenheit) colder than it is

currently and would be extensively glaciated and frozen. Another common greenhouse gas is CH4 (methane), which mainly derives from the decay of plant material in an oxygen poor environment such as Arctic tundra, peat bogs, deep ocean hydrates, and fossil fuel deposits.

Human disturbance of these deposits can release CH4 into the atmosphere.

CO2 Warming & Feedbacks As CO2 increases in the atmosphere, how much warming might the Earth expect? This question is where it gets complicated and contentious. Increasing CO2 alone is believed to produce about 1 deg-C of warming each time its atmospheric concentration doubles (e.g.

CO2 increasing from 200 ppm to 400 ppm can be expected to produce about 1 deg-C of extra global warming). However, that warming produced by CO2 initiates a chain of other processes that can affect the overall warming. These other effects are called feedbacks, and some can add to the warming produced by CO2, whereas others can subtract from it. One example of a complicated feedback is increased water evaporation into the atmosphere as temperature rises. That extra water vapor significantly cools the surface as it evaporates and itself increases the atmospheric greenhouse heating. But it also increases cloud formation, and some clouds reflect solar radiation back to space and thus tend to cool Earth.

Approximately 30% of solar radiation 5

incident on Earth is reflected back to space, and an appreciable fraction of this is caused by clouds. This effect of water as a feedback, especially with clouds, is poorly understood and regionally can be highly variable. Another feedback from CO2 warming is greater melting of land and sea ice, which permits greater adsorption of solar radiation and thus warming. Another variable produced by increasing CO2 is plant growth, for which CO2 is a necessary raw material. It has recently been documented that plant growth across the Earth has been significantly increasing, and this has been attributed to the increasing CO2 (and perhaps longer growing seasons and increased rainfall). As predicted future warming obviously depends on accurate predictions of future atmospheric CO2, increased plant growth could act to lower those anticipated CO2 amounts. As discussed below, estimates of the overall effect of feedbacks on warming is variable and controversial.

Natural Climate Factors As mentioned, the Earth receives energy from the Sun, loses that energy to space, and is further warmed by the role of greenhouse gases in delaying that energy loss. But there are other natural processes that influence Earth’s surface temperature by changing one of these three parameters. One dramatic process is variations in Earth’s orbit about the Sun that produces significant variations in

solar radiation received over time periods measured in several thousand years. Such orbital-caused effects were instrumental in producing past ice ages. Volcanoes emit some CO2, but perhaps sulfate aerosols they emit are more important to shortterm temperature changes. These aerosols (also produced by some human activity) reflect solar radiation and produce cooling, although the amount is still uncertain.

Significant correlation seems to exist between temperature over the past few centuries and solar activity as measured by sunspot numbers. Short-term variations (e.g. decades) in solar output of visible radiation (where the Sun emits most of its energy) is modest and not the sole cause of observed global warming over the past century. However, solar output at other energies is much more variable, and some have argued these contribute to global temperature change.

[The two most discussed solar variations are in the ratio of high-energy (UV) to visible radiation, which can change upper atmosphere albedo, and in energetic particle outflow, whose effect on cosmic ray flux is known to change particle ionization in Earth’s atmosphere and possibly alter reflective (higher albedo) cloud cover. Although strong circumstantial evidence exists for both processes, quantitative evidence for their influence on global temperature is lacking.]

Another factor producing shortterm temperature changes, which only recently has been appreciated, is ocean mixing. Because the oceans contain most of Earth’s near-surface heat and because their temperature varies significantly with depth, changes in vertical ocean mixing can and does change surface temperature sufficiently that atmospheric temperature 6

is affected. [The majority of solar radiation directly enters the oceans. The oceans readily influence atmospheric temperatures (e.g. via water evaporation), but transferring atmospheric heat into the oceans is more difficult.] Examples of the effect of oceans were demonstrated by El Nino events in 1997-98 and 2015-16, when warm water upwelling in the tropical Pacific significantly warmed global temperature, which later returned to near previous values. It is known that Ocean currents also have longer term mixing cycles (e.g. the AMO, Atlantic Multidecadal Oscillation, of about 60 years), which are poorly understood. The influence of these cycles on decadal global temperature variations may have been underestimated.

Whatever the cause, global temperature over the past few thousand years has varied by up to a few deg-C. One of the larger temperature changes was from the Medieval Period temperature high about 800-1000 years ago (when the Vikings settled Greenland), followed by a drop into the Little Ice Age a few hundred years ago (when western Europe and other regions experienced dramatically colder weather). For the past ~300 years global temperature has been increasing. Prior to the mid-20th century, these global temperature variations could not have been caused by CO2, which remained relatively constant. The Little Ice Age cooling does correspond to a lengthy period of very low solar activity, which has subsequently been increasing. This is suggestive, but does not prove, that solar output played a role in producing these temperature variations. The point is that there have been temperature variations over the past few millennia whose specific cause is not clear (but not due to changing CO2) and that these natural factors may

still be occurring and may be unrecognized.

How Much Future Warming?

Natural Basis.

With so many contributing factors, how can past climate data and current observations be used to predict the likely amount of future warming? Some researchers have noted that over the past couple centuries, global temperature appears to follow a regular cyclic pattern about 60 years in length and with a variation of a fraction of a deg-C. (Longer cyclic temperature variations of about a thousand years may also be present in the data.) Thus, it was warmer around year 1880, cooler around 1910, warmer around 1940, cooler in the 1960s, and warmer in the 1990s. Since the late 1990s, which might be part of a natural down cycle, atmospheric temperature has varied little.

The specific cause of this apparent variation is unknown, but may be one of the natural factors mentioned above.

However, a small but accelerating temperature increase appears to be superimposed on this cyclic temperature variation, particularly since the 1950s when the atmospheric CO2 increase accelerated. This acceleration of global temperature over the past half-century is consistent with an increasing greenhouse warming effect produced by CO2 and its feedbacks.

Models. Because neither the specific cause(s) nor the exact time pattern 7

of the apparent natural factors that have changed past global temperature are known, these past data cannot be accurately projected over the next century to predict future global temperature variations. Instead, official climate science uses very complex climate models run on powerful computers, similar to model calculations used to predict future weather, to predict future global temperature changes. Because decades to centuries are required to equilibrate new CO2 emissions among the reservoirs of atmosphere, oceans, and plant life, and because atmospheric CO2 has continually increased, these models are calculated under various assumptions for decades and centuries into the future. [Two common methods used in such models are the equilibrium method which assumes a one-time insertion of CO2 and wait until it has equilibrated before calculating the future temperature; and the transient method, which assumes a continual increase in CO2 at a prescribed rate.]

Such climate models require many input parameters that are either measured (e.g. weather data across the Earth’s surface) or approximated (e.g. natural factors as changing cloud cover). Another important input is an estimate as to how much future atmospheric CO2 will increase. This input requires both an approximation (guess actually) of what future human activities will be across various nations of the world and to what degree future sources and sinks of greenhouse gases may change (including how much and what type of fossil fuel will be burned).

Two important characteristics of predictions derived from these computer models are how widely variable their future temperature predictions can be, and how past model predictions have significantly over-estimated actual global

warming as measured for the atmosphere.

These climate models have not been verified in that their predictions have not been shown to be consistent with actual warming data over some period of time.

(Models can be made consistent with past climate data by adjusting model parameters after the fact.) Yet, it is future warming predicted from such models that drives official policy on climate change.

There is a growing belief that the CO2 climate sensitivity used in many of these models is too high. [A common definition of CO2 climate sensitivity is the degree of warming that would be produced by doubling the atmospheric CO2 concentration. The higher the CO2 sensitivity, the greater the predicted warming would be.] For example, the IPCC (International Panel of Climate Change) in their various reports have given the likely CO2 climate sensitivity as between 1.5 and 4.5 deg-C per CO2 doubling. However, some model runs predict CO2 climate sensitivities as high as 8.5. (Some model runs also assume future atmospheric CO2 growth rates will be twice that of the recent past and will continue throughout this century.)

Several more recent estimates of the CO2 sensitivity give values in the range of 1.52.0, and a few workers have suggested the sensitivity may be as low as 1. Climate models that utilize relatively low CO2 sensitivities project that over the next century atmospheric CO2 will only modestly increase, whereas the highest CO2 sensitivities predict atmospheric CO2 will triple. With climate models these options produce a wide variation in future temperature predictions. This emphasizes the importance of precisely knowing the correct CO2 climate sensitivity (especially feedbacks), a parameter which remains highly uncertain. “Official� climate 8

science often takes the average of many climate models showing wide variations in future global temperature. A critical question is whether the average of these models is more reliable than the individual models themselves.

There are four main points to be stressed about these climate models.

1) They are the only method employed in “official” climate science to predict future warming.

2) They require various input parameters, some of which are poorly known, and with the possibility that other important parameters are not being considered.

3) Accuracy of the CO2 climate sensitivity has not increased through the several IPCC reports over many years of consideration, yet the expressed IPCC confidence in future warming has increased.

4) Model-predicted future global temperature varies greatly among model runs and assumptions, generally overpredict warming rates, and leave considerable doubt as to what future global temperature actually will be under these assumptions.

What Are Possible Future Risks?

“Official” climate science has “declared” a dangerous upper limit to global warming of 1.5 to 2 deg-C (measured relative to a century ago, so we are half-way there), and claims that violating this limit will precipitate many predicted negative consequences, some of

which are mentioned below. This temperature “limit” is arbitrary.

Environmental changes that might be induced by global warming do not show identical sensitivities to rising temperatures, and the time period over which temperature rises (i.e., the temperature rise rate) is also an important factor. Further, most anticipated changes that might accompany warming do not suddenly appear at some temperature threshold, but rather proceed slowly as temperature rises. However, part of the concern is based on the fact that even if atmospheric growth of CO2 were to cease, some decades would be required for CO2 to equilibrate among reservoirs. In a dynamic system, it is not obvious that CO2 concentrations will ever fully equilibrate between oceans and atmosphere.

Those who express great concern about future warming base most of their concern on possible disruptive or catastrophic environmental conditions that they fear significant future warming might bring. Some of the warming risks are valid, whereas other suggested risks seem silly and petty. One of the highest concerns is that warming would melt the glacial ice covering most of Greenland and Antarctica, thereby raising sea level and flooding coastal land areas, where many of the world’s cities are located. About 120 thousand years ago, during the last interglacial period of the ice age (we are currently in another interglacial period), global temperature reached a few deg-C higher than today, part of these polar glaciers did melt, and sea level rose about 20-25 feet higher than today. Recent observations have noticed accelerated melting of parts of these ice caps.

Although not well defined, the sea level rise rate has been relatively constant for a century, indicating that the melting effect 9

is still quite small, no more than an inch a decade. [Determining global sea level, like global temperature, is not straightforward, and results can be uncertain.

Measurements are quite variable across different places, and in some places sea level appears not to be rising or even falling. The influence of tides, rising and sinking land near seashores, ocean expansion due to rising temperature, different effects of gravity, etc. all affect the sea level results.] The time required for melting the enormous volume of ice present on Greenland and Antarctica (both polar ice caps are 1 to 2 miles in thickness) to the extent that it occurred during the last interglacial is unknown but likely would require centuries. Thus, major flooding of coast lines is not an issue likely to soon occur, but it could occur eventually with continued increases in global temperature.

Recently, warming has been promoted as the cause of perceived increases in disruptive and violent weather. Many of these concerns have no observational basis, and for some just the opposite is true. For example, the number of Atlantic hurricanes has decreased (until very recently, no major hurricane had struck the US for a decade, a record) and the number of strong US tornadoes has decreased. Some weather patterns occur in time cycles across different regions of the world, e.g. droughts, and these may be confused with global changes. (The most intense documented drought in the US occurred during the 1930s, and earlier prehistoric US droughts have been identified.) Nevertheless, some weather changes predicted by global warming may be occurring. For example, warming increases water evaporation and thus rainfall, which may produce more intense rainstorms. The damage caused by

extreme weather such as droughts, floods, wildfires, etc., is commonly measured in terms of monetary losses that occur.

However, over time both human population and the number of human possessions and their monetary value increase. Thus, increased monetary losses from extreme weather would naturally occur, absent any increase in extreme weather events.

Many other possible risks of global warming often are mentioned by those greatly concerned. These include changing growth patterns for plants utilized for food (however, increased CO2 and temperatures have dramatically increased plant growth); movement of warm weather pests and diseases northward; increasing acidification of the oceans caused by dissolved CO2 (although natural pH variations across the oceans exceed the small reported pH increases); and others. It is popular among some climate scientists (and some non-scientists alike) to suggest virtually all kinds of perceived minor issues associated with future warming, most with very little or no evidence for support. In addition, the press (and environmental groups) often sees these issues as attention-grabbing for the general public and are more than ready to spread them with little to no verification.

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Possible Bias Effects.

We should be aware of potential bias associated with studies of environmental effects of global warming. For example, if a funding source funds a researcher to investigate the effects of increasing global warming on XYZ, there is a subtle influence imparted on the researcher to find some positive warming effect which needs to be investigated further. A negative finding would presumably cease the funding arrangement for that subject.

How the funding source posits the research goal is important to the result it obtains. In my opinion, for several years much of various federal agency support for environmental effects of future warming has significantly pre-biased the research by asserting beforehand that humans are causing dangerous warming. Such bias can extend far beyond the research itself and into how the research results are broadly interpreted and publicized.

Environmental organizations will believe the worse, and many members of the press see possible future catastrophes as subjects for good stories.

To summarize, some risks about future warming may be false; other risks associated with significant warming are real but likely will be slow to develop; some risks may be of future concern but are poorly understood; some suggested risks are not worth considering. In addition, future human action to negate some potential risks are likely. For example, for many decades US agriculture has been successful in developing new plant species that are more desirable than the old, and also are a solution to some natural “threat� to the plant. The whole topic of future potential risks deriving from global warming is both complex and

uncertain and needs much more evaluation.

How To Decrease Greenhouse Gas Emissions Whether produced by natural or human processes, or a combination of the two (most probable), it is likely that global warming, such as occurred over the past century, will continue to some degree.

Those who have strong concerns about future warming commonly argue that even if the degree of such warming and its possible consequences are uncertain, why not quickly phase out human production of CO2 around the world (and other greenhouse gases such as CH4) just to be sure, to be safe. Why take a risk about future warming? (Decreasing atmospheric water vapor, the major greenhouse gas, is not an option.) If the alternatives to generating CO2 were apparent, easy, quick, risk-free, and of inconsequential cost, this could be a compelling argument.

But they are not, as I now explore. This means that advantages of stopping generation of CO2 must be weighed against the disadvantages. Alternatives to those processes currently used to generate CO2 must be identified and vetted for suitability, and a suitable time period for accomplishing these changes must be examined. In some cases, it may be preferable to undertake mitigation action to control consequences of future warming. Again, the subject is complex.

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Greenhouse Gas Sources.

Production of CO2 and some other greenhouse gases in the US and the world derives from a diversity of sources. For the whole world, CO2 comprises about three-fourths of the total and CH4 (~16%) , nitrous oxide (~6%), and fluorinated gases the remainder. The major sources of world greenhouse gases are ~25% from electricity generation, ~24% from agriculture, forestry, husbandry, and other land use practices, ~15% from transportation, ~27% from industry and structure heating, and a few percent from other sources. The numbers are somewhat different for just the US. In the US, CO2 comprises 81%, CH4 11%, nitrous oxide 6%, and fluorinated gases 3%. The sources of US CO2 emissions are electricity generation 37%, transportation 31%, industry 15%, and heating and various other sources 16%. Major sources of US CH4 are ~42% fossil fuel extraction and ~50% from land use practices (all data from EPA). For the whole world, power generation and transportation are of less relative importance and various land use practices more important in comparison to the US. Countries that emit the most greenhouse gases are China (~23.5%), the US (~14.5%), India (~5.5%), followed by Russia, Brazil, and Japan at 3-5% each.

CO2 emissions are growing fastest in those nations developing most rapidly (e.g.

China, India, Indonesia).

Most of the advocacy for cutting greenhouse gas emissions has centered on CO2 from electrical power generation.

But, to substantially reduce greenhouse emissions, all of these major sources around the world must be addressed.

Over the past decade, the US has reduced its CO2 emissions more than any other major nation, and US emissions are currently equivalent to those in the early

1990s. This primarily has been accomplished by significant conversion of power generation from coal to natural gas (which liberates much less CO2 per unit of electricity generated) and by greater efficiencies in energy use, including transportation, insulation for heating, manufacturing, device operating efficiencies, etc. The US has also decreased its CH4 emissions through changes in land use practices, but CH4 leakage from newer methods of drilling oil & gas wells have increased in recent years.

(CH4 emissions also occur naturally, e.g. from organic deposits in the Arctic and methane-hydrates on the sea floor as these deposits warm.) A subtle factor in decreased CO2 emission shown by a developed country is outsourcing of energy-intensive industry (e.g., steel making, heavy manufacturing) to a less developed country, followed by import of the finished product back into the developed country. This practice simply transfers the CO2 production to another country.

Many developing nations around the world are rapidly increasing their CO2 emissions from power generation and transportation as they rapidly increase their standard of living. This emphasizes an important point. Even if the US cut its greenhouse gas emissions to zero, emission from other nations would continue to increase the global atmospheric inventory. To decrease CO2 and CH4 growth, virtually all nations would have to dramatically curtail greenhouse gases through major changes in agriculture, lifestyle, power generation, and transportation. Many of those nations give a much higher priority to increasing their standard of living, and it is not obvious that they would be either willing or able to cut emissions.

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What Are the Alternatives?

Emphasis for curbing CO2 emissions in the US and several other nations (e.g.

Europe, Australia) has focused on generation of electrical power through replacing the burning of fossil fuels (especially coal) with either natural gas or renewable sources such as wind and solar.

The US is rapidly replacing coal with gas in power generation, mainly because the relatively new drilling technique called fracking has enabled the production of abundant and cheap natural gas.

Conversion of current electrical power production in the US from coal to gas is, in principle, capable of reducing US CO2 emissions by another 12-15%. Although US wind and solar power have rapidly grown, these sources still only produce a few percent of US electricity. (See the next section for issues with wind & solar power.) Europe has not embraced natural gas and has even legislated against producing it internally, largely because of concern of negative issues associated with well drilling and fracking. (My personal opinion is that positive attributes of using natural gas far outweigh the negative.)

Some nations are increasing hydro power generation (which also does not release CO2), either by building new water reservoirs or converting old ones. But new reservoirs often are expensive and replace valuable land areas used for growing food, and they can be disruptive to the river and by forcing relocation of people. (Many environmentalists now advocate removing

dams on many streams.) Nuclear energy is only modestly increasing in some nations; however, a few nations plan significant future nuclear construction.

Nuclear has enormous potential for suppling reliable and continuous power with no CO2 emissions, but public concern about radiation (largely unwarranted in my opinion) has caused construction of new nuclear power plants to be very expensive and uncompetitive. In Germany, phasing out of nuclear, slowness to adopt gas, and grid problems arising from rapid increase of wind energy have caused increased use of coal for power and increasing CO2 emissions, in spite of Germany’s stated commitment to greatly decrease emissions. And the price of electricity in Germany is about three times that in the US. Some other nations are facing similar decisions. Using the probably false argument that burning wood is neutral for carbon emissions, a few nations have converted some coalburning power generation to woodburning (e.g. England, using trees largely harvested in the US). Not only does wood produce more CO2 than coal or gas per unit of energy generated, but it requires decades to regrow the harvested trees (thus recapturing the CO2 released upon the previous burning), and then only if effort and land are actually devoted to replanting trees. Thus, the short-term result of wood burning is increased CO2 emissions.

For the US to substantially decrease CO2 emissions beyond that achievable by replacing coal with gas, some argue for rapid conversion of transportation vehicles from petroleum to electricity.

However, converting to electrical vehicles requires substantial additional electrical power be generated by some means. If that extra electricity is produce in plants 13

fueled by natural gas, then many additional plants would have to be constructed and at considerable cost. If that electricity for transportation is produced by wind and solar, then the issues with these sources discussed below are compounded. Further, because of acquisition cost and vehicle lifetimes, a conversion to electrical transportation could not be accomplished rapidly. In addition, many facilities for recharging vehicle batteries, both at home and away, would have to be added.

Reducing greenhouse gas emissions even further also would have to address CO2 sources from land use and husbandry practices, manufacturing, heating, and device efficiency. Some CO2 reduction could be achieved in the last three categories, especially across the world.

But re-furbishing existing devices is expensive and unlikely to widely occur.

Land use and husbandry could probably be improved but would require effort and changes in lifestyle. (Some advocate curtailment of eating meat, especially beef, as husbandry both produces greenhouse gases and requires more land for its production compared to plants.)

It obviously would require considerable time, effort, and expense to make the conversions outlined above and quickly phase down greenhouse gas emissions. It also would require changes in many human lifestyle practices. Even a committed effort in the US likely would require a few decades to accomplish and is most unlikely to be cost neutral. [Official climate science (utilizing models discussed earlier) project that at current CO2 rates of increase, global warming of 1.5 deg-C (since late 1800s) could occur within a decade or two and 2 deg-C warming could occur within a very few decades.] How motivated would other

nations be to accomplish these CO2 reduction actions over the next few decades? Most developing nations view increasing their current low living standards as having higher priority over uncertain future warming. How does one convince a poor family in Africa or Asia without full-time electricity, refrigeration, clean water, and other amenities the US takes for granted that these are of less importance than reducing their future CO2 emissions? Global CO2 production is highly likely to continue to increase for at least a few more decades, independent of what the US and Europe may do to control it.

Issues with Wind & Solar.

Available and reliable energy made possible our modern societies, and the world increasingly demands lots of energy, preferably at relatively modest costs. If CO2 emissions must be greatly curtailed, it cannot readily be done by curtailing energy demand. Fossil fuels and CO2 emissions are viewed by many as undesirable, and there is little current incentive in the US (or Europe) to increase hydro or nuclear. Thus, many promote wind and solar. And if extensive conversion of transportation to electricity is done, power generation becomes by far the most important factor in controlling CO2 emissions. But not all sources of electrical power are equally desirable. The most valuable power is base-level, meaning the energy source can supply 14

energy needed when it is needed.

Normally coal-fired, gas-fired, hydro, and nuclear power sources provide energy 24/7 and can operate year-long with little down time. Further, nuclear and fossil fuel energy is concentrated, and power can be generated at a rather high efficiency rate, usually 80-90% or more. This power reliability is very desirable to a modern society. In some impoverished nations, electrical power is not reliable, which curtails such simple power uses as lighting, cooking, water purification, refrigeration, manufacturing, etc.

Wind and solar power are not baselevel because they do not produce power 24/7, and often they stop producing power suddenly and unexpectedly. Wind and solar are typically about 30% efficient.

Further, over short times wind and solar facilities may generate more power than is needed, requiring either that some facilities be stopped or that the unneeded power be dumped and wasted. In an electrical grid distributing power, it is very important that the demand for power be closely matched with power generation at all times. Otherwise, power brown-outs or blacks-outs or even damage to the grid can result. By contrast, fossil fuel, hydro, and nuclear facilities can generally match their power output to current and anticipated future energy demands. The fact that wind and solar power is not baselevel is critical in comparing relative costs of power generated by the various methods. Although wind and solar power sometimes can be produced as cheaply as that from coal and gas, that is only when these renewables are actually producing power and does not consider subsidies offered by many governments.

An important consideration occurs when wind and solar power suddenly are notavailable and must be supplanted by other

sources, e.g. fossil fuel power, thus requiring both the existence and operational readiness of another power source, such as coal, gas, or nuclear.

There are only two general ways to assure that wind and solar power alone can always supply available power in the quantity needed -- either store excess generated power for future use, or construct a grid large enough that power generated elsewhere is always available to places where power generation has stopped. Both of these methods have serious issues, as I now discuss.

Assuring Renewable Power Availability.

There are several envisioned means to store excess wind and solar power for future use when such power is not being generated. None are yet proven or widely used. These methods include battery storage, pumped hydro, gas compression to drive a turbine, gravity-driven weights, producing hydrogen gas (e.g. water electrolysis) for future burning, and others. All but the first two are mostly concepts with limited application.

Although battery storage may be a way to store modest amounts of power, batteries are expensive, currently use materials with possible limited availability, and their power storage capacities are so limited that enormous numbers of batteries would be needed for storing the significant power amounts the world requires. Batteries are useful for storing limited amounts of 15

power for short time periods, such as when renewable power fails and some time elapses before back-up (e.g. fossil fuel or diesel power) can be brought online. Development of battery technology is currently being driven by development of electric vehicles, which require compact batteries with large power storage capabilities. However, it is problematic whether battery storage of power for widespread use will occur within the next few decades.

An expansive electrical grid connecting many wind and solar facilities across a wide area is advocated by some to offer continuous power. However, across the US, solar does not produce power at night (or on very cloudy days), and wind sometimes stops blowing across a wide region. (Wind turbines actually require wind speeds within a certain range, neither too low nor too high.) So how large must a region of the US be to assure that the wind is always blowing somewhere? One analysis of western Europe found occasional times when the wind effectively quit across the whole area.

So, the area would have to be very large.

Also, if wind were blowing in one region but not another, both regions would require sufficient wind power generation capacity to supply both regions simultaneously, or twice the power capacity one region alone would require.

As the size of the one region where wind is blowing decreases relative to the whole region to be supplied at low wind times, the extra power generation capacity of any one region must be much more than twice what it alone requires. Much excessive generating capacity would be required compared to times when the wind was blowing everywhere. Further, electricity transmission across long distances requires extensive grid networks that do

not currently exist, and such long transmissions cause power to be lost. To me, it seems very impractical, likely impossible, to furnish reliable wind and solar power to a broad area by relying on an extensive grid network alone.

The erratic production of solar and wind power within a grid system mainly producing fossil fuel power also can produce issues. Either distribution of power systems and demand facilities must be shuffled, or output of some of the fossil fuel power systems must be rapidly changed. Rapid cycling of coal-fired power plants is difficult, and even for natural gas systems it can create issues and shorten plant life. In sunny urban areas where individual photo-voltaic power systems (roof panels) are common, solar may provide more power than is needed in the afternoon, but that power source rapidly diminishes as the Sun sets, thus requiring rapid acceleration in power output of the back-up system, commonly based on fossil fuels. [Newer combinedcycle gas plants are more efficient than older single cycle gas plants, but single cycle plants are better at rapid starts and stops desired for electrical back-up.]

Several percent wind/solar power generation within a grid system generally produces no serious issues, but that changes when these power sources reach several tens of percent.

Currently wind and solar power can be part of a generating system so long as a base-level system (fossil fuel, hydro or nuclear) is supplying power when wind/solar do not. Further, the number and capacity of fossil fuel power plants must be sufficient to supply power when wind/solar totally stop, and they must be staffed to accommodate such times. Thus, a portion of the fossil fuel systems mostly go unused but are required to be ready 16

when needed. This is not an efficient or economically desirable arrangement. The alternative is to not prepare for times when wind/solar do not produce and fossil fuel power is insufficient. Such periods would require suspending power supplied to some customers, either by brownouts, blackouts, or prior arrangements with some users to curtail power. Some cities and areas with rapid penetration of wind/solar power are pursuing this latter option. The extreme result of this technique could be that power is not always available to the user.

Another solution being studied is to develop efficient and economic means to store CO2 released by fossil fuel power plants such that it does not enter the atmosphere. Some small-scale experiments have been made to pump the CO2 under pressure into a deep underground reservoir where it would be contained. There are two major concerns with this process. First, whether longterm underground CO2 storage would be reliable, or would there be significant risk that the pressurized CO2 could be violently released to the surface. Second, is the question whether deep underground storage reservoirs sufficient to store the large quantities of CO2 produced in power plants even exist. Another concept under study is to convert gaseous CO2 into a solid to facilitate storage. This idea has not advanced beyond the lab experiment stage.

A SUMMARY PERSPECTIVE It is not my intent here to argue for one of the extreme views about growth of atmospheric CO2 and future warming – whether it is all human caused and will shorty create serious problems for societies, or whether it is at least partly natural and, at least in the short-term not a serious issue. (My view leans toward the latter.) Also, it is not my intent here to answer whether wind and solar power can efficiently and cost-effectively replace fossil fuel power in order to significantly reduce future CO2 emissions within a reasonable time period. Rather, my purpose is to demonstrate that throughout the debate there exist many uncertainties and decision points. Further, any attempt to reduce future greenhouse gas emissions must address the entire world, not just the US, and if climate model predictions are correct, such actions must occur within decades. It would be foolish to ignore these issues. On the other hand, it would also be foolish to embark on expensive mitigation efforts that disrupted society and were later shown to be ill-advised and unnecessary.

It may be the case that much of recent global warming was due to natural causes and that CO2 climate sensitivity is relatively low. In that case much of the expressed concern over climate change may be false. If most global warming is caused by CO2 emission (and not variable natural forcing) and if the CO2 climate sensitivity for increasing temperature is relatively high, then it appears impractical, likely impossible, to limit global warming to less than a few deg-C over the next several decades. Attempts to do so would require massive effort and expense, not just for the US, but most nations of the world, and such attempts are likely to fail. Efforts in some countries 17

to date are not encouraging. Further, it is likely that some efforts now underway or planned to control warming will not be productive, and new ideas will have to be pursued. All this will require time and expense. Society has time to fully evaluate various issues associated with global warming before deciding what significant actions may have to be taken, actions that may themselves produce negative consequences.

Relevant to the above viewpoint is this quote from the AR5 report of the IPCC. “To conclude, the vast majority of the raw observations used to monitor the state of the climate contain residual non-climatic influences. Removal of these influences cannot be done definitively and neither can the uncertainties be unambiguously assessed.�

The one position I do advocate here is that all entities around the world involved in the global warming issue step back, listen to other points of view, consider all conceived options and costs, and begin a general debate with the broader public. It may be the best approach is to take no rash action now, learn more, and develop contingency plans. Such plans could include mitigation against possible and undesirable future warming effects should they arise. They might not arise, or new, better ideas may be revealed. Or future warming may prove not to be a serious issue. ***************************************

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