On Friday, the Intergovernmental Panel on Climate Change (IPCC) released a summary of the biggest report on climate change since 2007. The final draft will be unveiled Monday.
The world’s top climate scientists are more certain than ever that climate change is real and humans are causing it.
“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia,” the report said. “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 new report says with at least 95% confidence that human-emitted greenhouse gases are responsible for most of the Earth’s warming since 1951. Scientists were only 90% confident in 2007, and the human contribution to global warming wasn’t even mentioned in the first report, published in 1990.
Here are some of the key findings:
Atmospheric levels of carbon dioxide have increased by 40% since the industrial revolution, mostly from fossil fuel emissions.
Most of that carbon dioxide is released into the atmosphere, but about
30% of emissions are absorbed by the ocean. The pH of sea water is lowered as it takes in more carbon, making the world’s oceans more acidic. Ocean acidification is
blamed for killing coral reefsand other
As concentrations of carbon dioxide have increased, so have land and ocean surface temperatures. Combined global land and ocean surface temperature show an average warming of 0.85 degrees Celsius between 1880 and 2012.
Due to natural variability, trends based on short records do not accurately reflect long-term climate trends. Scientists point out that the rate of warming in the past 15 years has been small compared to the rate since 1951.
A long view, however, shows that each of the past three decades have been successively warmer at the Earth’s surface than any preceding decade since 1850.
If carbon emissions continue unchecked, scientists predict that average temperatures between 2080 and 2010 will be 2.6-4.8 degrees Celsius higher than today.
Warming temperatures will lead to changes in the global water cycle.
“The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions,” the report said.
As global surface temperatures rise, it is very likely that spring snow cover in the Northern Hemisphere will continue to decline and Arctic ice will continue to shrink and thin.
Northern Hemisphere snow cover has fallen by 11% each decade since 1967, while Arctic sea ice has been melting by 9-14% each decade since 1979.
Melting sea ice will cause sea levels to rise. Global seal levels have risen by roughly 8 inches in the last century. One model suggests that sea levels could further rise by 3 feet in the next one hundred years if nothing is done to curb CO2 emissions.
Even if CO2 emissions are stopped, the effects of climate change will continue for many centuries.
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