A look at climate change

By Kenneth G. Hubbard

Informed businessmen, including farmers and ranchers, are asking, Can short- to long-range planning/decisions be aided by accounting for climate variability and global warming trends? Indeed, all citizens may ask what elected officials are doing with regard to current and future climate while puzzling over how government remedies will affect federal and possibly state and local commerce. Will new legislation result in increased taxes or increased regulation, and will the biggest carbon dioxide producers bear the bulk of any costs to reduce carbon dioxide (CO₂)? In addition, depending on the nature of federal policies, the costs of producing goods and services could increase as well. On the other hand, a do-nothing policy may be very costly. These questions are beyond the scope of this communication, but clearly no intervention or a lack of mitigation may lead to undesired consequences, depending on the “degree” to which the climate changes.

Let’s examine the records. On the scale of the last 100 years, the concentration of CO₂ in the atmosphere has risen sharply on the order of 25 percent. (See the graph labeled CO₂, where ppm means parts per million.) This increase is largely due to the industrial revolution and industry’s dependency on the burning of fossil fuels.

The CO₂ concentrations during man’s recorded history have been among the highest in the past 400,000 years, where the prerecorded records are determined from ice coring and other geological records. The development of industry (in all countries) was the obvious cause for the recent rise in CO₂.

At locations where a sizeable annual cycle in temperature is observed and conditions are otherwise ecologically favorable to plants, the atmospheric CO₂ will decrease starting with spring growth of vegetation (low point in September and October), corresponding to the increased rate of CO₂ used in photosynthesis. This phenomenon has been identified as a potential means of sequestering CO₂ and storing it in the soil, thereby decreasing the CO₂ in the atmosphere. Permanent storage of CO₂ is somewhat difficult to attain; although plants tend to mine the CO₂ from the atmosphere, the gas is released back to the atmosphere from the plants during nighttime. Further release from the soil occurs in fall and winter as photosynthesis approaches zero. The peak concentration is usually April through June. This is what one would expect in the northern hemisphere. Because the southern hemisphere has comparatively little land area, the vegetative cycle of the northern hemisphere dominates the annual cycle of CO₂ around the globe. The resulting seasonal oscillation in CO₂ concentrations can be seen in the figure but only from the late 1950s forward, as monthly data is not available prior to that time.

Due to the relatively low concentration of CO₂ in the atmosphere (about 0.03 percent), it is referred to as a trace gas. Even though CO₂ represents a small fraction of the atmosphere, it contributes strongly to the greenhouse effect. CO₂ and other gases change the energy balance of the earth in such a way that the earth’s surface is much warmer with the atmosphere present than it would be with no atmosphere or with an atmosphere that contained no greenhouse gases. So, some CO₂ in the atmosphere is a very positive thing. This is because the radiation from the sun is fundamentally different from the radiation given off by the earth’s surface, and greenhouse gases are more transparent to the sun’s energy. Thus, greenhouse gases allow much of the sun’s energy to pass through the atmosphere and reach the surface. The greenhouse gases absorb a portion of the energy radiated up from the earth’s surface, bringing the gas molecules to a higher energy state. The result is more radiation emitted from these molecules. Instead of all of the energy escaping to space through the atmosphere, a portion is emitted in the direction of the earth’s surface. Recent increases in atmospheric CO₂ are irrefutable, and the fundamental interaction of CO₂ with energy is a well-known process in the atmosphere. And to repeat, the recent increase in atmospheric CO₂ is largely the result of increasing industrial development. The use of fossil fuels has increased during this period, and CO₂ is one of the byproducts of combustion.

Has the increase in CO₂ influenced the atmospheric temperature? The global mean surface temperature anomalies (difference between annual global temperature average for a given year and the long-term average for the globe) for both land and ocean show an increase. The increase has been on the order of one degree celsius per century. In the past century, there is a period when temperatures did not rise. This period was from about 1950 to 1980 when the lack of warming, in light of the continued increase in CO₂ concentrations, is puzzling. It raises the possibility that other climate forcings are at times compensating for the warming. Some forms of natural climate forcings are solar variations, volcanic activity, earth orbital variations and ocean/land coupling.

There is some evidence of an increase in both CO₂ and surface temperature. When two curves rise and fall in the same manner, it may be coincidental; however, in this case we have physical processes that explain a linkage between the two. Unfortunately, the two curves do not always respond in the same way. For instance, the increase in the CO₂ from 1950 to 1980 is clear, but the temperature during that same time period shows neither warming nor cooling.

This leads us to conclude that there are other factors that must, at times, control the slope of the temperature curve. Does this make the call for action less compelling?

If we accept that there are other factors at work, it doesn’t negate the reality that changes in the concentration of a trace gas like CO₂ will change the atmospheric energy dynamics. With the complexity of the atmosphere and the variety of feedbacks in the atmosphere (for example, what if the change in surface temperature causes more cloud convection that results in more cloudiness and leads to more blocking of the sun’s energy?), it is by no means easy to predict the future of the atmosphere. Even the driving force of atmospheric energy, the sun’s output, is known to change in rhythm with sunspot activity.

Scientists have set out to predict future climates. It is a particularly challenging task, because the processes in the atmosphere are highly nonlinear. What this means is that the best mathematicians in the world, using all available mathematical tools, cannot obtain an exact solution to the future state of the atmosphere. In the absence of mathematical solutions, climatologists have turned to the computer for help. The complex equations and processes that represent the atmosphere are coded into the computer to form a model of the atmosphere. The model is integrated forward in time from an initial state. In the formation of these computer models, many processes have been simplified. The question is whether these simplifications and the coefficients introduced into the computer models will produce a realistic future state of the atmosphere. Likewise, the models do not provide a high spatial representation but, because of computing limitations, focus on points that are hundreds of miles apart. The modeling community concedes that no one day in the future will match the same day in the models but suggests that the future climate (integration of all days) will be adequately predicted. These models, that are similar in many ways, do predict a future climate warming of the atmosphere.

The Intergovernmental Panel on Climate Change (IPCC) published an assessment of the state of knowledge with regard to the question of climate change. The IPCC report (Climate Change 2007) consists of three volumes addressing the Physical Science Basis; Impacts, Adaptation and Vulnerability; and Mitigation of Climate Change. The lead authors of the report shared a portion of the Nobel Peace Prize. The following is taken from Volume One of the 2007 IPCC report. This is what the IPCC authors wanted policymakers to know.

*Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750. The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land use change, while those of methane and nitrous oxide are primarily due to agriculture.

*The increased understanding in the past several years have led to a very high confidence that the global average net effect of human activities since 1750 has been one of warming.

*Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

*Long-term changes have been observed in arctic temperatures and ice, precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather, including droughts, heavy precipitation, heat waves and the intensity of tropical storms.

*Some aspects of climate have not been observed to change, e.g., the range in daily temperature, Antarctic sea ice extent, and small-scale phenomena such as tornadoes, hail, lightning and dust storms.

*Paleoclimatic studies (studies of climate taken on the scale of the entire history of Earth) support the interpretation that the warmth of the last half century is unusual in at least the previous 1,300 years.

*Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (man’s activities are the source) greenhouse gas concentrations.

The consequences of climate variability on the Plains have been and continue to be justification for this work. Climate change (from fossil fuels) is really a subset of all climate variability. The concept that well-informed decision makers will make better decisions and well-informed policymakers will make better policy motivates scientists to better understand the impacts of climate. To help understand the climate system, the University of Nebraska-Lincoln has expanded its role in climate monitoring, climate data quality control, climate and vegetation, assessing climate impacts, and determining relevant information for public policymakers and decision makers. Building on these strengths the university is in a position to build a program of excellence in the area of climate change.

This article urges the scientific community, the political officials and the public to agree that CO₂ could be a major influence relative to natural variability in the climate.

The best immediate course of action to take, if CO₂ is a major influence relative to natural variability in the climate, is to make policy and decisions to support society’s well-being through the stewardship of the environment. The policies and strategies gained will be useful in light of natural variability, regardless of our future findings related to man’s influence on climate. In particular “no regrets” policies should be considered so as to ameliorate man’s impacts on the environment, while at the same time avoiding sweeping changes where the economic consequences may be unacceptable. Few would support a global-scale experiment related to releasing chemicals into the environment. Can we defend a global and unplanned experiment wherein CO₂ in the atmosphere is increased by combustion of fossil fuel?

Bookmark/Search this post with:

Delicious  •   Digg  •   StumbleUpon  •   Facebook  •   Yahoo