Rapid Climate Change Overview, Executive Summary
Nick Perry, July 2007
Climate change ranks as the preeminent danger to modern human civilization today. The evidence for significant warming since the Industrial Revolution 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.
1. The Climate System
A basic understand of the climate system is necessary to understand and situate climate change. The climate system is the complex network of interconnected and interactive systems that controls the earth’s climate. There are three particularly relevant aspects of the climate system with global warming: radiative forcings, the greenhouse effect, and positive feedback loops.
1.1 Radiative Forcings
Radiative Forcings denote an externally imposed perturbation in the energy budget of the Earth’s climate system, meaning that something is causing a change in the total energy level of the system. 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, which is expressed as heat on the surface, and radiative forcings are a quantitative measure that represents this stress on the system.
1.2 The Greenhouse Effect
The greenhouse effect is created by the collection of atmospheric gases surrounding the Earth that traps a percentage of the radiation leaving the surface, and re-radiates back towards Earth. This absorption holds energy in the Earth system, causing warming and maintains the Earth's surface temperature at a level necessary to support life. Increases in the levels of greenhouse gases in the atmosphere cause more radiation to be absorbed and creates warming.
1.3 Positive Feedback Loops
Positive feedback loops magnify and amplify stresses and changes to the system, because they feed back into themselves. Also called “snowball effects”, these loops arise from the complex interconnectivity of the climate system, and can cause small variations or changes in the climate to have much larger and often unforseen implications.
2. Scientific Evidence of Warming
The basic evidence for the existence of substantial global warming is undeniable given the modern collection of evidence and observations.
2.1 Contemporary Empirical Evidence
The basic level of data is the measures of increasing average global temperatures, which have increased 1.36°F (0.76°C) over the last 100 years. This data correlates to other direct measures of atmospheric water vapor, mountain glaciers, snow cover, sea level, and average ocean temperature, which all show distinct measures of climate warming. A secondary level of data consisting of regional observations, 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 all add further evidence for warming because of their connection through the complicated climate system.
2.2 Paleoclimate Empirical Evidence
Paleoclimate observations through tree ring and temperature proxies such as δ18O ice core data show evidence of contemporary warming on a longer timescale. Additionally, the paleoclimate readings show that the post Industrial Revolution warming period is an anomaly given the established climate trend over the last 400,000 years, which shows that based upon the trend the Earth should be moving in a cooling direction following the warming spike directly after the last glacial maximum 20,000 years ago, but instead the earth is warming.
3. Causes and Drivers of Climate Change
3.1 Standard Anthropogenic Argument
The broadly accepted argument of warming is that the post-Industrial Revolution warming of the atmosphere is based upon increased greenhouse gas emissions from anthropogenic sources. There is a distinct correlation through the greenhouse effect between atmospheric levels of carbon dioxide and methane and the global temperature levels because of the greenhouse effect. The increased gas levels are a byproduct of some 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. The evidence for distinct rises in the levels of carbon dioxide and methane from anthropogenic sources represent the two largest climate forcings. An international scientific consensus has centered on this causal story, and now represents the prevailing scientific opinion for the cause and driver of climate change.
3.2 Alternative Explanations
There are multiple complementary and alternative opinions that attribute the causality of climate change elsewhere. 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. A second alternative theory is that warming is based upon heat generated by human waste heat, via the second Law of Thermodynamics, and that the order and complexity of modern existence puts off sufficient heat to warm the atmosphere. A third alternative approach makes a variety of assertions, including 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, in rejecting the greenhouse gas driven explanation.
4. Consequences of Climate Change
The current modeling based projections of the effects of climate change are catastrophic and place it as the single greatest threat to humanity today. The direct political, social, economic, and environmental ramifications are indeed calamitous. The latest modeling projections predict the following potential consequences of modern warming: a high degree of warming, a high rate of warming, biodiversity loss, sea level rise, a threat to insurance industry and capital markets, a threat to food supplies, a threat to water supplies, a threat to human health, increased risk of conflict, a threat of societal instability, amplifying feedback effects, and a danger of a runaway effect. These scenarios are only exacerbated by the realistic possibility of “sleeping giant” feedback loops, runaway effects, and unknown impacts.
5. Conclusions
The basic understanding surrounding the global warming issue is that warming since the Industrial Revolution is undeniable, it is being driven by human causes, and it presents a distinct threat to the earth’s climate system. Global warming is a definitive reality created by human actions, and it connects at a fundamental level with the other greatest problems facing society. Climate change ranks as the single greatest threat to modern society, and the future results will be cataclysmic without effect policies to control the human destruction on the climate.
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