Secret reasons to rapid climate change in the future

On Earth, the current rate of increase of carbon dioxide in the planet's atmosphere, it is likely that a few degrees increase in average temperatures and large changes such as loss of ice sheets that could lead to several meters of sea level rise this century. New research into the Earth's paleoclimate history of NASA's Goddard Institute for Space Studies director James Hansen, the potential for rapid climate change in this century, including several meters of sea level rise if global warming has not abated.

Looking at how the Earth's climate in the past responded to natural changes, Hansen sought views on the fundamental issue of ongoing human-induced climate change: "What is a dangerous level of global warming?" Some international leaders have suggested objective of limiting warming to two degrees Celsius (3.6 ° F) from pre-industrial times to avoid catastrophic change. However, Hansen said at a press conference at the American Geophysical Union meeting in San Francisco recently, the warming of two degrees Celsius (3.6 ° F) would lead to drastic changes such as significant loss of ice sheets in Greenland and Antarctica.

Depending on the temperature analysis work on Hansen's Goddard Institute for Space Studies, Earth's average global surface temperature has already risen 0.8 degrees Celsius (1.4 degrees Celsius) since 1880, and is now warming of more than 0.1 ° C (0.2 ° Fahrenheit) every ten years. This warming is largely driven by increased greenhouse gases in the atmosphere, particularly carbon dioxide emitted by burning fossil fuels in power plants, cars and industry. At the current rate of burning fossil fuels, the concentration of carbon dioxide in the atmosphere doubled before the industrial revolution in the middle of this century. Doubling of carbon dioxide would cause any warming of several degrees, Hansen said.

In recent research, Hansen and co-author Makiko Sato, also of the Goddard Institute for Space Studies, compared climate today, "Holocene", similar to previous "interglacial" periods - the time when the polar ice caps existed, but the world is dominated by glaciers. In the study of cores drilled from both ice sheets and deep ocean sediments, Hansen found that the average global temperature during the "Eemian" period that began about 130,000 years ago and lasted about 15,000 years, less than 1 degree Celsius (1.8 ° F) warmer than today. If the temperature rose two degrees Celsius (3.6 ° F) above pre-industrial times, the average global temperature much higher than in the Eemian, when sea level was four to six meters higher than today.

Paleoclimate record reveals a much more sensitive to climate than thought, even as several years ago. Limitation of human-caused warming of two degrees [C] is not sufficient, "said Hansen." It would be a recipe for disaster. "

Hansen has focused much of his new work on how the polar regions, and especially ice sheets in Greenland and Antarctica will respond to warming of the world.

Two degrees Celsius (3.6 F) warming the Earth much warmer than the Eemian, and would move closer to the Earth "Pliocene" type, when sea level was in the range of 25 meters (82 feet) higher than today, said Hansen. When using the earth's climate history to find out more about the level of sensitivity that govern our planet is warming in response to today paleoclimate Hansen suggests that each degree Celsius global temperature will ultimately equate to 20 m (66 ft) sea-level rise. This, however, sea level rise due to ice sheet loss could be expected over the centuries, and great uncertainty as to remain in predicting that the loss of ice would unfold.

Hansen points out that ice sheet disintegration is not a linear process. The nonlinear damage has already occurred in sensitive places such as Pine Island Glacier in West Antarctica, where the rate of mass loss of ice continued to accelerate in the last decade. Restoring data from NASA's Gravity and Climate Experiment (Grace), the satellite is already in compliance with the speed of ice sheet mass loss in Greenland and West Antarctica, which doubles every ten years. GRACE record is too short to confirm this with great certainty, but the trend of recent years, does not it, Hansen said. This continued rate of decline of the ice could cause more meters of sea level rise by 2100, said Hansen.

Ice cores and ocean sediments from the polar regions suggest that temperatures at the poles in past epochs - when sea level was several meters up - not too far from the Earth's temperature could be achieved in this century to 'business as usual "trajectory.

"We have substantial cushion between today and dangerous climate warming," Hansen said. "The earth is going to experience strong amplifying feedbacks in response to a further slight global warming."

Details of the warming of the new goals and how to get there, are outside the scope of this research, Hansen said. But this research is consistent with earlier findings Hansen is that the amount of carbon dioxide in the atmosphere would be back from about 390 ppm in the atmosphere of 350 ppm today to stabilize the climate in the long term. While officials continue to discuss a framework for reducing emissions, global emissions of carbon dioxide remained stable or increased in recent years.

Hansen and others noted that while paleoclimate evidence paints a clear idea about what on earth before the weather looked, but using it to precisely predict how the climate may change in much less time, in response to man-made rather than natural climate change is becoming increasingly difficult. But Hansen said that the Earth is already showing signs of responding, even if the "slow feedback", such as changes in ice sheet.

Issue of human-caused increase in the amount of carbon dioxide into the atmosphere, the climate is also something never seen in 65 million year record levels of carbon dioxide - a drastic growth rate, which is difficult to predict how fast the Earth will respond. At a time when carbon dioxide has increased due to natural causes, an average rate of increase of 0.0001 ppm per year - in other words, one hundred parts per million in a million years. Combustion of fossil fuels, now the concentration of carbon dioxide increased to two parts per million per year.