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New Report Says Climate Change Irreversible for Next 1,000 Years

A newly released study says the effects of climate change may be irreversible for the next 1,000 years.

The study published Tuesday in the journal Proceedings of the National Academy of Sciences says that even if carbon dioxide emissions are reduced the effects on global temperature could remain high for generations.

The study led by researchers at the United States National Oceanic and Atmospheric Administration says that possible climate changes include global sea level rise and reduced rainfall in certain parts of the world.

Scientists said those changes could decrease water supplies, increase the frequencies of fires, expand deserts and affect agriculture.

Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research, says that while scientists have known about the effects of climate change, the new study provides new details as to the specific effects.

"Scientists have known about some irreversible aspects of climate change for some time," said Kevin Trenberth. "But what this paper does is help to highlight these aspects and quantify some of them, and I agree with the authors that this aspect is one which is relatively poorly appreciated by policy makers and probably the general public and it is a real concern."

The scientists say that oceans are currently slowing down global warming by absorbing heat, but they will eventually release the heat back into the air leading to a greater warming of the planet. The study says that that warming will lead to a loss of ice sheets in Greenland and Antarctica contributing to an overall rise in sea levels.

Trenberth, who was not involved in the study, says he believes that it underestimates global warming's effect on sea levels.

"In the past five years Greenland has been melting at rates that are higher than they consider in this paper, and it's been adding about 0.5 millimeters per year to sea level rise," he said. "If Greenland melted, it would certainly take something like 850 years, or something like that, but the time to restore it would take 10 times that long, it would take 10,000 years. And once it's gone its hard to reverse it and put it back."

Before the industrial revolution, the earth's air contained about 280 parts per million of carbon dioxide. That number has since risen to 385 parts per million.

The study says that if CO2 levels peak between 450 and 600 parts per million the results over the coming century would include a dry-season rainfall in the Mediterranean, southern Africa and southwestern North America comparable to what was seen during the "Dust Bowl" era of the 1930s.

Patrick Michaels, a global warming skeptic with the CATO Institute, says there has been an increase in rainfall over the southwestern United States during the warming of the planet over the last 100 years. He says the study is highly speculative about the effects of climate change in the future.

"The problem with this paper is that it is a speculation for 1,000 years and we don't know what the energy structure of our society will look like 100 years from now, probably not even 50 years from now," said Patrick Michaels. "Surely if this paper is right it's saying that you can't do very much about warming."

But Trenberth disagrees and says that any action taken now will prevent the effect of climate change from being worse.

"There are a number of changes that are very likely to happen that will be in practical terms not reversible, but it doesn't mean that if we don't take actions now that it wont have effects, it mean that if we keep going on our current path without even reducing and lowering emissions of carbon dioxide and other greenhouse gases that the climate changes would be even bigger and worse or longer lasting," he said.

Scientists say carbon dioxide emissions account for nearly half of all greenhouse gases in the atmosphere. However, other gases such as chlorofluorocarbons and methane also contribute to global warming.