In the last decade our understanding of climate change has vastly increased and the debate surrounding climate change has been settled. Notwithstanding the natural variability of the Earth’s climate, top scientists from all the major scientific bodies of the world are unanimous about this man-made phenomenon. They have stated unequivocally that global warming is occurring, and people are causing it by burning fossil fuels (like coal, oil and natural gas) and cutting down forests. All agree that we must take immediate action to avoid the most dire consequences of global warming.

• The U.S. National Academy of Sciences, which in 2005 the White House called "the gold standard of objective scientific assessment," issued a joint statement with 10 other National Academies of Science saying "the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action. It is vital that all nations identify cost-effective steps that they can take now, to contribute to substantial and long-term reduction in net global greenhouse gas emissions."
• In February of 2007 the Intergovernmental Panel on Climate Change ("IPCC") issued its report concluding that "[g]lobal atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. . . . 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 IPCC report went on to state that "[w]arming 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 . . . Among its findings:

• Eleven of the last twelve years (1995-2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850).
• The linear warming trend over the last 50 years is nearly twice that for the last 100 years.
• The average atmospheric water vapour content has increased since at least the 1980s over land and ocean as well as in the upper troposphere. The increase is broadly consistent with the extra water vapour that warmer air can hold.
• Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system. Such warming causes seawater to expand, contributing to sea level rise.
• Mountain glaciers and snow cover have declined on average in both hemispheres. Widespread decreases in glaciers and ice caps have contributed to sea level rise (ice caps do not include contributions from the Greenland and Antarctic Ice Sheets).
• New data now show that losses from the ice sheets of Greenland and Antarctica have very likely contributed to sea level rise over 1993 to 2003.
• Global average sea level rose at an average rate of 1.8 mm per year over 1961 to 2003. The rate was faster over 1993 to 2003: about 3.1 mm per year.

In terms of understanding and attributing climate change, the report stated that "[m]ost of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR’s [Third Assessment Report’s] conclusion that 'most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.' Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns . . ."

The science of global warming is clear

While greenhouse gases occur naturally, scientists confirm that recent and relatively rapid increases in greenhouse gas emissions stem from human activity related to our energy use. In other words, the primary cause of global warming is carbon dioxide emitted into the atmosphere through the burning of fossil fuels like gasoline, coal, oil and natural gas, which we use as energy to power our cars and homes and to produce the goods we consume.

Energy-related carbon dioxide emissions from coal, petroleum and natural gas represent 82% of total U.S. human-made greenhouse gas emissions. Methane (from agriculture, landfills, coal mines, and oil and gas operations) represents another 9%. Nitrous oxide (emitted from burning fossil fuels and through the use of certain fertilizers and industrial processes) represents another 5% of total greenhouse gas emissions. Other human-made gases (released as byproducts of industrial processes and through leakage) account for another 2% of greenhouse gas emissions.

In summary, the science of global warming is clear. The only debate in the science community about global warming is about how much and how fast warming will continue as a result of heat-trapping emissions. Scientists have given a clear warning about global warming, and we have more than enough facts — about causes and fixes — to implement solutions right now.

References:

• Joint Statement of Science Academies: Global Response to Climate Change,. 2005.
• Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change: Summary for Policymakers, February, 2007 (emphasis added).
• Energy Information Administration, Grenhouse Gases, Climate Change and Energy (modified 4/2/04), found at: http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html.