“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased…The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years.” IPCC Fifth Assessment Report (AR5) – Climate Change 2013: The Physical Science Basis.
The Intergovernmental Panel on Climate Change (IPCC) just released the first part of its Fifth Assessment Report on climate change, which is authored by the world’s foremost climate experts.
It found that the evidence of human influence on the climate has grown since the last assessment in 2008. While scientists typically avoid declaring 100 percent certainty on anything, the report concludes that “it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.” The phrase “extremely likely” equates to between 95 percent and 100 percent certainty.
A medical diagnosis from just one doctor where he or she expresses 95 to 100 percent certainty would warrant action for most people. Here we have hundreds of experts on the earth and its atmosphere saying that it is sick and that they are 95 to 100 percent certain of the cause.
The report states:
“Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.”
Prudence would dictate that we take this diagnosis seriously and start doing what we can to reduce our greenhouse gas emissions.
The IPCC report, a summary for policy makers, fact sheets and other information can be found at:
The full IPCC Fifth Assessment report will be comprised of contributions from three “Working Groups.” The portion just released is from Working Group I and addresses the physical science basis for climate change. It has 209 Lead Authors, 50 Review Editors from 39 countries, and more than 600 Contributing Authors.