PFEL-Climate Change & Global Warming 4

Is the Earth’s Climate Warming? (Is Global Warming Real?)

The debate on the reality and degree of global warming and man's role and responsibility in this process extends from the scientific community to the global political arena, with a variety of viewpoints. It is widely accepted that the Earth’s climate, including global and regional temperatures, fluctuate naturally on a wide range of time scales extending out to centuries and millennia. Climate researchers also have demonstrated an accelerated global warming trend during the last 150 years, coinciding with the Industrial Revolution. There is some disagreement about the amount of this warming, and even whether it is real or an artifact of observational error or bias.

The cause of this warming is also the subject of some dispute. The consensus of scientists and governmental climate agencies in many countries is represented by the United Nations Intergovernmental Panel on Climate Change (IPCC) assessments that conclude "An increasing body of observations gives a collective picture of a warming world and other changes in the climate system". Other scientists believe this change is due primarily to natural fluctuations unrelated to human influences. As climate researchers continue to quantify the magnitudes and fluctuations of natural climate changes, and understand the mechanisms responsible for these changes, they narrow the uncertainty about how human activity has affected the global climate.

What Could Cause Global Warming?

The greenhouse effect is essential in keeping the Earth warm enough for life. The process known commonly as global warming could be a consequence of growing levels of greenhouse gases, most notably carbon dioxide (CO₂). These gases trap some of the energy going out from the earth and redirect it back to the earth's surface. Water vapor is by far the most important greenhouse gas, accounting for over 90% of the natural greenhouse effect. However only small increases in the other greenhouse gases, such has occurred over the past century, can warm global temperature via the amount of heat trapped in the atmosphere. While CO₂ concentrations in the atmosphere have varied naturally over geological time scales, the burning of fossil fuels by humans is the overwhelming source of increased atmospheric CO₂ in recent times. Methane, produced by increased rice cultivation and livestock production, is another greenhouse gas. Others include chlorofluorocarbons (CFCs), which are artificial compounds associated with refrigeration and soil fumigants, and nitrous oxide - for example smog - from internal combustion engines. Recent studies indicate that these non-CO₂ greenhouse gases have contributed significantly to climate change in recent decades.

Long-term variations in other factors – solar energy emission, volcanic gas and dust levels, and the storage and redistribution of heat in the deep ocean – impact the Earth’s climate and may produce a global warming trend. Separating the role and degree of human impacts from natural variation in climate remains a complex and challenging scientific question. But it is important to realize that, whether natural or human-induced, climate variability is large enough to impact marine populations as well as our own lifestyles. A critical question is whether human activity is altering the climate more rapidly than ecosystems and society can adapt. A second question is to what degree that civilization is willing – and able– to adapt to the combined effect of natural and anthropogenic climate change.

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