95%
2013 September 27
95%, that’s the figure scientists involved in the latest United Nation’s Intergovernmental Panel on Climate Change (IPCC) are using to express their degree of certainty that human activities are contributing to an “unequivocal” rise in global temperatures, according to reporting by the BBC.
Today, Working Group I of the IPCC (based in Stockholm, Sweden) released its Fifth Assessment Report (the first was released in 1990) on the current state of scientific knowledge relevant to climate change. Working Groups II and III (based in Tokyo and Berlin) will release their assessment reports in 2014.
Key statements in the report Summary for Policy Makers include the following:
“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.”
“Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years.”
“Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 (high confidence). It is virtually certain that the upper ocean (0−700 m) warmed from 1971 to 2010.”
“Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass,
glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent (high confidence).”
“The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901–2010, global mean sea level rose by 0.19 [0.17 to 0.21] m.”
“The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have
increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.”
“Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750.”
For more information, here is a link to the IPCC homepage.
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