The global warming debate or global warming controversy is an ongoing argument about the increase in the global average air temperature that has occurred since the middle of the twentieth century. People on various sides of the global warming debate dispute the cause and meaning of this observation. For one thing, they disagree about whether the warming trend is part of a cycle of climatic variations that have existed for millennia on the one hand, or a product of intensified greenhouse gas emissions caused by human activity. They also argue about what the effects of global warming are likely to be, as well as which, if any, steps should be taken in response to global warming, with suggestions ranging from a dramatic reduction of greenhouse gas emissions to doing nothing.
Global warming, or climate change—which is considered to be a more neutral term, was a matter of concern in Europe in the 1980s. Concern spread, and the United Nations Framework Convention on Climate Change (UNFCCC) responded with the Kyoto Protocol of 1997, aimed at stabilizing greenhouse gas levels in the atmosphere to “prevent dangerous anthropogenic interference with the climate system.” The Kyoto Protocol was, notably, ratified by all member states of the European Union, but not by the United States, which merely signed it, a gesture without meaning. But at one time, the United States was an outlier.
At the end of the first decade of the twenty-first century, what at one time had appeared to be a consensus that anthropogenic or human-made carbon emissions are responsible for the current climate change had eroded and renewed the global warming debate. Reports indicate that as June, 2009, over 700 scientists disagree with the U.N. climate summary created for policymakers in 2007, including some who contributed to the report. Other scientists who were not involved with the report but who once believed in human-made global warming have also recanted.
There are a variety of possible reasons for the renewed global warming debate. One is that weather data since 2001 reveals carbon dioxide in increasing concentrations while the temperature has not increased. This contradicts that understanding of the relationship between carbon emissions and climate. Another is that the economic downturn of 2008–2009 led to a re-evaluation of the scientific studies, since cutting carbon emissions would cause important changes in industries and further damage the economy. Thirdly, new peer-reviewed research has questioned the predictions about the expected effects of climate change, with regard to important issues such as melting of the polar ice caps, rising oceans, and spreading disease.