by Peter Gleick, water and climate scientist, in a Forbes repost
These facts are just part of why all national academies of science on the planet and every major geophysical scientific society agree that humans are fundamentally changing the climate.
CO2 in the atmosphere continues its inexorable rise
The heart of the climate problem is that our burning of fossil fuels along with other human activities have thrown the atmospheric levels of greenhouse gases out of balance, and their concentration in the atmosphere is growing faster and faster. This classic record from Mauna Loa in Hawai’i shows the growth in the CO2 concentration in the past half century. But it’s worse than that: CO2 concentrations in our atmosphere are now higher than at any time in the past million years, and perhaps higher than in the past 15 million years.
The concentration of carbon dioxide is higher today than in a million years.Higher concentrations of greenhouse gases leads to a hotter planet
As CO2 (and other heat-trapping gas) concentrations have risen, so have planetary temperatures, just as basic physics and models predict. Here are the land and ocean surface temperatures for the past 130 years as measured by scientists at NASA (first figure) and NOAA/NCDC (second figure), confirmed by independent scientists internationally. While temperatures go up and down, the long-term trend is indisputably up. 2011 was the 35th consecutive year since 1976 that the yearly global temperature was above average. La Niña cooled the global average temperature in 2011 by quite a bit, but it was still abnormally hot. Indeed, 2011 was the hottest “La Niña” year ever recorded.
A hotter planet means an intensification of the hydrological cycle
One of the consequences of global warming, predicted from basic physics and models, is more water in the atmosphere and more rainfall globally (with increases in both wet and dry extremes). And observations of the real worldhave shown these projections to be happening.
Globally, 2011 was the 2nd wettest year over land on record since 1900 (and the wettest year was just one year earlier: 2010). Drier than average conditions were widespread across much of French Polynesia, the Solomon Islands, Hawaiian Islands, northwestern Canada, and southwestern China. The wettest regions included much of Central America, Micronesia, northern Brazil, and the northeastern U.S.
A hotter planet means disappearing glaciers and ice, especially in the Arctic.
Ice in the Arctic continues to thin and disappear, even faster than anticipated. Arctic sea ice extent during September 2011 (the month when ice is at a minimum) was nearly 35 percent below the 1979–2000 average — the second smallest September Arctic sea ice extent since precise records began in 1979,according to the National Snow and Ice Data Center. And it wasn’t just September: overall, 2011 Arctic ice extent (that bottom blue line) was far below the long-term average for every single month.
The extent of Arctic ice in 2011 was lower, in every single month, than the long-term average.
A warming planet also means more extremes of climate.
Anyone watching or reading the news or looking out the window probably had a sense that 2011 was a weird year with one bad, extreme weather disaster after another. It was. As the climate changes, scientists anticipate more extremes, and the reality around us confirms that. Here are two graphs: the first from NOAA shows the fraction of the United States in either extreme drought or extreme flood over the past century: 2011 had the highest fraction ever recorded — nearly 60% of the country. The second, also from NOAA, shows that 2011 had the largest number of weather/climate disaster events exceeding a billion dollars ever — 14 of them, even adjusting for inflation.
— Peter Gleick is a member of the National Academy of Sciences