Rapid Climate Change Overview

Rapid Climate Change Overview

Nick Perry, July 2007

Climate change…is a problem that is, at last, both universal and personal for every human on the planet. Climate change makes moot past environmental issues precisely because it isn't about an obscure species or remote place. It's about us, and our fate. It is about the real possibility of the unraveling of modern civilization.

Climate change ranks as the preeminent danger to modern human civilization today. The evidence for significant warming since the Industrial Revolution[2] is now irrefutable and undeniable. It is an immensely complex issue, with vociferous proponents on each side of the debate, however a scientific consensus has emerged attributing causality to human actions. It is seminally important to the future of humanity because it intimately intertwines with the other great problems facing humanity today and has profound impacts on political, social, economic, and environmental levels. The general purpose of this paper is to provide a broad and instructive overview of the climate change issue. The sections that follow will serve the following primary functions to provide an overview of this seminal issue:

1. Define the climate system and outlining three particularly relevant aspects of the climate system to consider during the climate change debate.

2. Establish the fundamental evidentiary basis for the existence of climate change, both in the contemporary and paleoclimate contexts.

3. Outline the broadly accepted anthropogenic-induced argument, and then presenting some of the various counter-arguments to this prevailing view.

4. Present a projection-based summary of the effects of continued climate change on both ecological and human scales, based upon the most recent model projections.

5. Summarize the main argument surrounding the global warming, and situate the issue in a modern context of interconnectivity with the other biggest problems facing society.

Relevant Aspects of the Climate System of the Earth

In order to discuss the observations, evidence, and arguments surrounding contemporary climate change, it is first necessary to define a few basic concepts crucial to understanding the Earth’s climate system. According to the Intergovernmental Panel on Climate Change[3] (IPCC), the climate system is a “highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere, and the interactions between them”.[4] The climate system itself evolves over time under the influence of internal and external changes and exists in a state of dynamic equilibrium. Studying the climate system is a complex and arduous task, but in the terms of the modern global warming trend three fundamental concepts emerge; radiative forcings, the greenhouse effect, and positive feedback loops in the interconnected global system. Examining these concepts, even in a limited context, builds an underlying understanding of the drivers on the climate system and the potential impacts on contemporary climate change.

1.1 Radiative Forcings

The fundamental concept of radiative forcings plays a major role in modeling and examining climate change. The IPCC places particular emphasis on radiative forcings, which they define as “a measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism.”[5] An alternate and less complicated IPCC definition reads “to denote an externally imposed perturbation in the radiative energy budget of the Earth’s climate system.” [6] The contemporary period is defined by a positive imbalance between the quantity of the sun’s energy absorbed by the Earth’s atmosphere and the amount of energy emitted back into space by the planet. The system at all times attempts to achieve thermodynamic equilibrium, equating the amount of energy leaving and entering. Because the law of conservation of energy states that the total amount of energy in an isolated system remains constant, an increase in either the amount of energy entering the system or the amount of energy retained in the system would create a positive forcing. For example, in the modern period more energy comes into the system than radiates back into space, which drives a net climate forcing. The forcing creates the rudimentary impetus for global warming, because the additional energy in the system manifests itself as heat. Radiative forcings describe the stresses on the climate system and so frame the scientific evidence for global warming and the debate over its causes, whether anthropogenic or otherwise.

1.2 Greenhouse Effect

A second relevant scientific concept is the greenhouse effect, particularly because it is generally regarded as the driving causal force behind the anthropogenic-induced global warming argument. A given percentage of light energy from the sun passes through the atmosphere and enters the Earth-atmosphere system. In turn, the land and oceans release infrared radiation (heat) into the atmosphere, balancing the incoming energy. The collection of atmospheric gases covering the Earth traps some of this radiation and re-radiates it in all directions, with a percentage of it sent back towards Earth. This absorption holds energy in the Earth system and maintains the Earth's surface temperature at a level necessary to support life. Without heat-trapping greenhouse gases, the surface of the Earth would have an estimated average temperature of -18°C rather than the rough current average of 15°C.[7] The greenhouse effect with relevant energy values are shown in Figure1.2.1.

Figure 1.2.1 - The Greenhouse Effect

Source: http://www.greenhouse.crc.org.au/about_greenhouse/greenhouse_effect.cfm

The greenhouse effect becomes highly relevant to the climate change discussion because the efficiency of infrared radiation absorption by the atmosphere and re-emitted back toward earth is a function of the insulating envelope of greenhouse gases (GHG) in the atmosphere. The greenhouse gases include water vapor, carbon dioxide, methane, and various other ozone gases, so the prevalence of these substances in the atmosphere creates a powerful control mechanism on the overall radiative forcing of the earth system. Human activities such as burning fossil fuels emit vast quantities of GHG, providing the basis for arguments that humans are causing global warming.

1.3 Positive Feedback Loops and Interconnectivity

The third fundamental notion in understanding climate change is the feedback loops operating in Earth’s complex and interconnected climate system. The earth system subdivides into a myriad of interacting subsystems that weave together into a network. In models of contemporary warming nearly all of the systems known to affect climate change contain positive feedback loops that amplify stresses and changes to the system, and can also be referred to as “snowball effects”. A positive feedback loop does not mean that the affect necessarily creates warming, but rather that the impact of a stress to the system (in either direction) is magnified and reinforces itself. The feedback mechanisms relevant to global warming are complicated and numerous, and include greenhouse gases (primarily CO2, NH4, N2O, and halocarbons), water vapor concentration, cloud effects, Albedo effects, aerosol concentrations, evaporation levels, geothermal heating, and others. These mechanisms are typified by Figure 1.3.1, which shows a sample feedback loop.

This feedback system operates in the following manner; rising global temperature melts surface snow and ice, which lowers the general Albedo of the surface (a ratio of a substance’s reflectivity to electromagnetic absorption) because white surface snow has a much high reflectivity than the underlying dark earth. The newly exposed soil absorbs more sunlight than the snow and re-emits the light as infrared radiation that warms the globe and creates a further rise in temperature.

Additionally, not all feedback loops are positive loops leading to further warming. Aerosol concentrations (primarily sulfate, organic carbon, black carbon, nitrate, and dust) in the atmosphere create a net cooling effect.[8] A complete scientific understanding of the Earth’s intricate feedback systems is still incomplete, but observational data and increased modeling continue to accentuate the role of these mechanisms in controlling global temperature and climate change. The climate feedback mechanisms create the opportunity and possibility of rapid climate change by enabling unpredictable, non-linear fluctuations in the climate system. While steady climate change presents a developing peril to humanity, the realities of a world under a situation of rapid climate change could be potentially disastrous on a very immediate timescale. The complex feedback system and the inherent unpredictability and non-linear potential this creates must be considered during any discussion of the causes of global warming.

Overview of the Prevailing Scientific Evidence of Warming

A vast quantity of observational climate indicators and baseline scientific evidence supporting modern global warming has been accumulated. When viewed independent of causal mechanisms, the observational and evidentiary support for global warming now stand as undisputable. This is evidenced seminally by the IPCC in stating that “warming of the climate system is unequivocal, as is now evident from observations of increases in global air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”[9] The evidence for warming simply cannot be denied; the Earth’s temperature is rising at an alarming rate, as the following evidence clearly elucidates.

2.1 Contemporary Empirical Evidence

At a basic level, the temperatures at the Earth's surface increased by an estimated 1.36°F (0.76°C) over the last 100 years. This shows a profound change in the temperature of the earth, while not historically unprecedented, is certainly statistically significant. Additionally, 11 of the last 12 years rank among the 12 hottest years in the instrumental record (since 1850)[10], and the hottest 22 years on the record all have occurred since 1980.[11] Furthermore, average atmospheric water vapor content over land and ocean and in the upper troposphere has increased since at least the 1980s, consistent with warmer air’s ability to hold extra water vapor. Mountain glaciers and snow cover have declined on average in both hemispheres, and global sea level rise has been documented at an average rate of 1.8 mm per year from 1961 to 2003 and 3.1 mm per year from 1993 to 2003.[12] This further combines with the fact that the average temperature of the global ocean has increased to depths of at least 3000 meters and that the ocean has been acting as a large heat sink absorbing more than 80 percent of the heat added to the climate system.[13]

The IPCC also stated that “at continental, regional and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.”[14] These secondary level observations, derivatives of the interconnected nature of the climate system, add another layer of complexity to the empirical evidence for change. The empirical evidence for modern warming is essentially irrefutable, so the only meaningful discussion addresses the causal mechanisms, and the ramifications of global climate change.

2.2 Paleoclimate Empirical Evidence

Paleoclimate studies analyze and interpret climate changes over a time scale that can extend back millions of years. Primarily through proxy studies, exemplified by tree rings (size of growth correlates to general climate favorability) or deuterium δ18O ice core data (a temperature proxy), humans can gain a perspective on contemporary warming. Over the history of the earth, the paleoclimate record indicates alternating periods of warming and cooling. While all paleoclimate observations are susceptible to some level of variability and error, IPCC’s statistical confidence intervals indicate that the modern warming is extremely unusual in at least the previous 1,300 years[15]. Additionally, the last time the polar regions, where climate variability is greatest on a paleoclimate scale, were warmer than today was approximately 125,000 years ago.[16] Evidence from the Vostok ice core has allowed scientists to use the δ18O proxy to established a large saw tooth pattern on an approximately 100,000 year scale consisting of a slow descent into an ice age climate followed by an abrupt warming, projected back over the last 400,000 years.[17] This sawtooth pattern is shown in Figure 3.1.1. The last glacial maximum was approximately 20,000 years ago followed by the typical abrupt warming period, but after a brief period of cooling, the contemporary warming period interrupted this historical cycle. This means that without intervention of some kind, the paleoclimate pattern projects that the Earth should be experiencing a progressively cooler climate. The paleoclimate data is another supplemental component that provides further evidence to the reality and relevance of modern global warming.

Causes and Drivers of Contemporary Climate Change

3.1 Standard Anthropogenic Argument

The large scale scientific consensus is that the observed global warming is due to human causes, primarily through the emission on large levels of greenhouse gases in modern industrial period (essentially since 1850). These increases are a byproduct of the most basic functions of the modern way of life, including fossil fuel combustion, industrial processing, and changes in land use, such as deforestation. Typifying this argument, Science magazine has stated that “without substantial disagreement, scientists find human activities are heating up the Earth’s surface.”[18] This conclusion is based upon the work of Naomi Oreskes, a historian of science at the University of California, San Diego, who evaluated 928 scientific papers that dealt with global climate change and found that none disagreed about human-generated global warming.[19] The IPCC measures a number of factors affecting climate change and assesses them by their radiative forcing (RF) measurement. Each factor is assigned an RF number[20], with positive numbers denoting an increase in global temperatures and a negative number denoting a decrease in global temperatures. The following components form the basis of the case for human-induced warming as presented by the IPCC and are summarized in Figure 3.1.2:

· Carbon dioxide (CO2) emissions have an RF number of 1.6, making them the most significant contributor to climate change through its interaction as a highly receptive greenhouse gas. The greatest single source of carbon dioxide emissions is the burning of fossil fuels, although changes in land use also contribute. Since pre-industrial times carbon dioxide concentrations in the atmosphere have increased from 280 ppm[21] to 370 ppm.[22] This is an astronomical increase of 32% on a minute time frame given the earth’s , and projections based upon human usage are for further increases into the future. The 2005 reading far exceeds the natural variance measured in ice cores for the last 650,000 years, indicating anthropogenic responsibility for creation of extremely high levels of carbon dioxide in the atmosphere. The variance of carbon dioxide over the last 425,000 years and its close correlation to global temperature is summarized in figure 3.1.1.

Figure 3.1.1

Source: Data adopted from National Oceanic & Atmospheric Administration <http://www.noaa.gov/> Accessed at: <http://www.seed.slb.com/en/scictr/watch/climate_change/causes_co2.htm>

Over the past 425,000 years cool periods have coincided with times when the CO2 concentration in the atmosphere was lower and when there is less CO2 in the atmosphere the greenhouse effect is reduced and the world cools. The blue and red line indicates the variation in average global temperature compared with the 1961-1990 average. The green line shows the concentration of CO2 in the atmosphere, which in the modern period has spiked to unprecedented levels. The saw tooth pattern of glaciations is consistent with the orbital cycles of the Earth over the last 400,000 years, but the pattern has been interrupted by modern global warming. [23]

• Methane (CH4) emissions have an RF number of 0.48. Agriculture generates most methane emissions, and since pre-industrial times methane concentrations have increased from 715 ppb[24] to 1774 ppb.
• Ozone depleting chemicals[25] have an RF number of 0.35.
• Halocarbons have an RF number of 0.34.
• Nitrous oxide emissions have an RF number of 0.16.

All of the above variables contribute to a warming of the global climate. Their combined effect along with the addition of several small factors totals an RF number of 3.14. The following variables all contribute to a cooling of global temperatures.

• The emission of aerosols[26] has an RF number of -1.2. The direct reduction of radiative forcing is responsible for -0.5, while the indirect creation of cloud cover is responsible for -0.7 RF because the atmospheric Albedo increases, blocking incoming radiation before it gets inside the earth’s atmospheric system.
• Human induced changes in land cover have an RF number of -0.2 due to a decrease in the general Albedo effect of the earth.

These two factors have a combined RF number of -1.4, and when that is added to the RF number associated with factors causing global warming the final RF number is 1.87. However, due to uncertainties in the data the IPCC report is based upon, they conclude that an increase in RF is likely closer to 1.6 RF, in summarizing their the findings in favor anthropogenic induced warming argument. Figure 3.1.2 presents a visual rendition of the summary of the RF numbers.

While the IPCC does not specify an exact correlation between RF and temperature, Dr. James E. Hansen of the NASA Goddard Institute estimates that the earth’s sensitivity is 0.75±0.25 °C per watt/square meter of climate forcing.[27] The IPCC report also concludes that there is a greater than 90% chance that the rate of industrial era greenhouse gas radiative forcing is “unprecedented in more than 10,000 years,” and most fundamentally that the “globally averaged net effect of human activities since 1750 is one of warming.”[28]

3.2 Alternative Explanations

While the vast majority of scholars agree that human actions are causing global warming, there are other theories attempting to explain global climate change that should be recognized. One of the best-supported theories maintains that human are simply not significant enough and cannot have a profound enough impact on the global climate system to cause global warming. Thus, something bigger must be going on, such as the sun heating up and warming the entire solar system. Evidentiary support for a version of this theory can be found in recent studies done by Swiss and German scientists, headed by Dr. Sam Solanki, that note that for the last 100 to 150 years the Sun has burned more brightly than at any time during the past 1,000 years.[29] However, while some make the argument that “global warming has finally been explained: the Earth is getting hotter because the sun is burning more brightly”, many supporters of such experiments only see increased solar radiance as another factor that can be added to anthropogenic causes in explaining global warming, not an independent causality.[30] Bill Burrows exemplifies this view in stating that “while the established view remains that the sun cannot be responsible for all the climate changes we have seen in the past 50 years or so, this study is certainly significant.”[31]

Dennis Bushnell, a Chief Scientist and NASA’s Langley Research Center, champions a second complimentary explanation to the greenhouse gas approach. He presents a theory of warming based upon heat generated by human waste heat using the second Law of Thermodynamics. Operating with a mind focused on the future, he finds that even if greenhouse gases and feedback loops were held constant at modern levels, human existence itself on earth would still create global warming. His theory uses a nontraditional model of anthropogenic heating, arguing that warming results from the heat wasted as highly evolved organisms progress up the ladder of energy necessity in a world of imperfect efficiency. He claims that the second Law of Thermodynamics requires the production of prodigious amounts of waste heat associated with human energy utilization. He calculates that even without greenhouse gases, the surface temperature would increase by margins of multiple degrees in the near future. Similar to the solar system heating argument, Bushnell’s assertions are not mutually exclusive with anthropogenic greenhouse-driven warming.

A third set of alternatives differ from the first two in the fundamental way that they cannot coexist with the greenhouse gas dominated anthropogenic argument. The proponents make a variety of assertions, which include claims that climate change is not significant enough to be anything more than random fluctuations, that there are still legitimate scientific evidentiary disputes, or that actions to correct warming will cause unacceptable economic damage. A prime example of a distinguished scientist who takes this stance is atmospheric physicist Fred Singer, who is a Distinguished Research Professor at George Mason University, professor emeritus of environmental science at the University of Virginia, and is president of The Science and Environmental Policy Project. [32] He summarizes his opinion on climate change by stating that “human activities are not influencing the global climate in a perceptible way, and that, in any case, very little can be done about global climate. We should not even try to influence it. Climate will continue to change, as it always had in the past, both warming and cooling on different time scales and for different reasons, unrelated to any human action.”[33] While only a small minority of scientists dissent from the standard anthropogenic model of global warming, examining alternate models and can expose weaknesses in the prevailing argument.

Consequences of Warming

If the current warming trend continues into the future, the environmental consequences will be catastrophic. It is imperative to understand that these consequences are based upon projections and speculation, and therefore should not be accepted on the same level as empirical evidence. The systems for predicting the effects of climate system have shortcomings due to the complexity and variable interconnectivity of the networks, but ongoing research and development have allowed increasingly accurate modeling and projections. The potential consequences that follow are all subject to some level of uncertainty and questioning because of the modeling shortcomings, the evidentiary support is mounting and they are based upon consensus opinions and distilled from research gathered from climate scientists around the world. The 12 damaging projections presented here are distilled from IPCC, and adapted from the succinct presentation by Jeremy Leggett in his book Empty Tank[34]:

· A high degree of warming. Projected future temperatures will be too high for many ecosystems to tolerate potentially causing instability, fluctuations, and failure.

· A high rate of warming. Projections have unabated rates of change at dangerous levels for ecosystems and humans alike.

· Biodiversity loss. Coral reefs and tropical rainforest, which stand as two of the most diverse ecosystems in the world, are likely to suffer most as temperatures rise.

· Sea level rise. A combination of thermal expansion of oceans and melting of polar ice caps in Greenland and Antarctica threatens coastal communities worldwide. 50 percent of the world’s population lives within 50 miles of the coastline, so a rise in sea levels could cause massive loss of life and global migrations on an unprecedented scale.[35] Even a small rise in sea levels would cause crises; take the vulnerable delta region of Bangladesh, where 30 million would be left homeless by a mere one meter rise in sea level.[36]

· A threat to insurance industry and capital markets. A powerful characteristic of climate change that is truly only now becoming a reality is the potential impact it has on the already fragile financial system. A prime example is the vulnerability of a single coastal state, Florida, with around 2 trillion dollars of insured assets. The insurance industry maintains a reserve of approximately on half a billion dollars to cover all catastrophic losses worldwide. If the assets of Florida were severely damage, the prospects of an industry-wide failure appear very real, with profound implications for all of society. A single catastrophe could erase billions or even trillions of dollars in assets, shaking the foundation of the increasingly integrated global market and triggering a chain reaction causing global socioeconomic damage. The Stern Economic Review addresses the broader economic ramifications of warming, stating that “global warming constitutes the greatest failure of market economics”, and estimates “that if we don’t act, the overall costs and risks of climate change will be equivalent to losing at least 5% of global GDP each year, now and forever. If a wider range of risks and impacts is taken into account, the estimates of damage could rise to 20% of GDP or more.”[37] Moreover, in addressing the further ramifications, the Review stated that “our actions now and over the coming decades could create risks … on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century.”

· A Threat to food supplies. Global warming can cause both floods and droughts, put heat stress on crops, and give pests access a wide range of areas that were too cold for them to survive before. The booming human population is already straining food supplies, and rising sea levels may cut off access to fertile costal soil, with all of these ramifications synergizing to making the prospect of global famines very real.

· A Threat to water supplies. Warming has already begun depleting aquifers and causing other compounding effects. For example with particular ramifications is the dependency of China and India on the depleting glacial melt from the Himalayas. The glaciers, which regulate the water supply to the Ganges, Indus, Brahmaputra, Mekong, Thanlwin, Yangtze and Yellow Rivers, are believed to be retreating at a rate of about 10-15m (33-49ft) each year. [38] This threatens the water supplies of western China, Nepal, and Northern India, where approximately one third of the globe’s populations lives. In the western hemisphere, the burgeoning cities of Lima in Peru and Santiago in Chile both depend on meltwaters from the dying glaciers in the Andes.[39] Additionally, warming causes greater evaporation from lakes and reservoirs and changes global precipitation patterns, threatening the water supplies of the entire globe.

· A Threat to human health. Exemplified by the spread of areas where disease-bearing insects, notably mosquitoes, can survive, because places that freeze once a year have much lower disease rates due to annual die-offs. Scientists at the American Society for Microbiology meeting in Toronto directly connect environmental changes to the possible “spread of infectious diseases such as: Malaria, Yellow fever, Meningococcal meningitis, Hantavirus, Influenza, and Diarrheal disease.”[40]

· Increased risk of conflict. Many major river basins run through two or more countries, exemplified by the Tigris-Euphrates Basin, the Indus Basin, and many others, and growing scarcity only leads to heightened tensions. The possibility of “water wars” and other conflicts is only exacerbated by social and economic effects of warming.

· Amplifying feedback effects. Based upon the feedback loops addressed earlier. Possibilities include melting permafrost, drying soils, dying forests, stratifying oceans, and melting methane hydrates, all of which create huge levels of uncertainty and may push the true effects past even the worst IPCC projections.

· A Danger of a runaway effect. The worst-case analysis shows a point of irreversibility, where warming started by human activity is overtaken by warming caused by the climate system’s natural feedback loops. Once global warming reaches the point of irreversibility no human action could prevent the planet from continuing to heat to unknown levels. Current projections have set a critical danger threshold at 2.0°C above the pre-industrial temperature, creating a foreboding doom on the horizon if action is not taken.[41]

One final component of the consequence discussion that needs to be directly addressed is the realistic possibility of profound rapid climate change. There exists numerous “sleeping giants”, specific natural aspects of the climate system which could set of powerful feedback loops on a very short time scale, meaning months or years. A few examples of these potential rapid change inducing feedback are as follows: methane hydrate destabilization, soils causing land biosphere to turn from absorber to emitter, the North Atlantic “ocean conveyor belt” shuts down, the Greenland ice cap melts, or the west Antarctic ice sheet slides into the sea, as well as other geographically specific events in vital locations such as the Amazon, the Tibetan plateau, and the Sahara.[42] While it is not the prerogative of this paper to go into each of these possible scenarios, each one is in fact backed by legitimate scientific evidence. The difference between these sleeping giants and other basic feedback loops becomes a matter of time and scale; the giants could develop far faster than humans can react to control them, or their impacts might be so large that there would be no possibility of an effective human counter effort. These may come across as outlandish doomsday forecasts and likely will not all come to fruition, however their presence alongside the litany of other trend-based effects creates a legitimate basis to prescribe a necessity of action to halt the contemporary warming trend.

Conclusion

On a fundamental level, climate change ranks as the preeminent danger to modern human civilization today. The evidence for significant warming since the Industrial Revolution is incontrovertible and undeniable. It is an immensely complex issue, with vociferous proponents on each side of the debate, however a scientific consensus has emerged attributing the root causes to human actions. Understanding this issue and the way intimately intertwines with the other great problems facing humanity today sheds light on its profound implications on political, social, economic, and environmental levels. There is an immediate and perilous necessity of action to induce change, particularly given the understanding of feedback loops and the real possibility of rapid climate change as humanity crosses an irreversibility threshold, and with every moment the necessity for change only grows.

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