Thursday, January 24, 2008

American Geophysical Union says climate is out of balance

[x-posted on The Two Dollar Bill]

Add in another 50,000 concerned scientists from 137 countries to the rolls of those who believe in climate change or global warming.

The AGU (American Geophysical Union) issued a statement saying

changes in temperature, sea level and rainfall were best explained by the increased concentration of greenhouse gases from human activities...

The AGU also suggested that carbon emissions should be cut by 50% within the next 100 years (by 2100).

In 2003, the AGU called for greater understanding of climate change, but didn't go as far as to say definitively that global warming was occurring... much less suggest necessary steps to reduce the effects or point the finger at the causes of global warming.

And in the statement, the AGU clearly puts forth blame on the human population.

During recent millennia of relatively stable climate, civilization became established and populations have grown rapidly. In the next 50 years, even the lower limit of impending climate change—an additional global mean warming of 1°C above the last decade—is far beyond the range of climate variability experienced during the past thousand years and poses global problems in planning for and adapting to it. Warming greater than 2°C above 19th century levels is projected to be disruptive, reducing global agricultural productivity, causing widespread loss of biodiversity, and—if sustained over centuries—melting much of the Greenland ice sheet with ensuing rise in sea level of several meters. If this 2°C warming is to be avoided, then our net annual emissions of CO2 must be reduced by more than 50 percent within this century. With such projections, there are many sources of scientific uncertainty, but none are known that could make the impact of climate change inconsequential. Given the uncertainty in climate projections, there can be surprises that may cause more dramatic disruptions than anticipated from the most probable model projections.

With climate change, as with ozone depletion, the human footprint on Earth is apparent. The cause of disruptive climate change, unlike ozone depletion, is tied to energy use and runs through modern society. Solutions will necessarily involve all aspects of society. Mitigation strategies and adaptation responses will call for collaborations across science, technology, industry, and government.

This comes in to the hopper today along with news that Antarctica is melting much faster than previously thought. And fast enough not that glacial melt is making massive pools under the ice sheet... and outpacing Greenland in the phase change.

Two processes are speeding the melt there:

  1. As ice melts and makes glacial pools, it absorbs more sunlight than the icepack... and heats up at a faster rate.... helping to chip away at the icepack with an ever increasing rate.

  2. As the ice pack breaks off or calves into the ocean, the ice farther inland isn't held back as it once was... and increases the rate of motion toward the sea.
On the other end of the world, some suggestions by scientists are that the Arctic will feature ice-free Summers by 2013.

From the BBC:

...But it is has become apparent in recent years that the real, observed rate of summer ice melting is now starting to run well ahead of the models. The minimum ice extent reached in September 2007 shattered the previous record for ice withdrawal set in 2005, of 5.32 million square km. The long-term average minimum, based on data from 1979 to 2000, is 6.74 million square km. In comparison, 2007 was lower by 2.61 million square km, an area approximately equal to the size of Alaska and Texas combined, or the size of 10 United Kingdoms.
While melting sea ice will mean a redistribution of ocean water at higher levels world wide, it does have very interesting implications for world trade. Shipping lanes from Northern Canada, Alaska, Russia and beyond will emerge for at least a few months... something we've never seen in the modern age.

Still, the unknown looms. Even recently updated computer models aren't keeping up. Professor Peter Wadhams of Cambridge University is an expert Arctic ice and notes

"In the end, it will just melt away quite suddenly. It might not be as early as 2013 but it will be soon, much earlier than 2040."

The US National Snow and Ice Data Center (NSIDC) collects the observational data on the extent of Arctic sea ice, delivering regular status bulletins. Its research scientist Dr Mark Serreze was asked to give one of the main lectures here at this year's AGU Fall Meeting.

Discussing the possibility for an open Arctic ocean in summer months, he told the meeting: "A few years ago, even I was thinking 2050, 2070, out beyond the year 2100, because that's what our models were telling us. But as we've seen, the models aren't fast enough right now; we are losing ice at a much more rapid rate.

"My thinking on this is that 2030 is not an unreasonable date to be thinking of."

And later, to the BBC, Dr Serreze added: "I think Wieslaw is probably a little aggressive in his projections, simply because the luck of the draw means natural variability can kick in to give you a few years in which the ice loss is a little less than you've had in previous years. But Wieslaw is a smart guy and it would not surprise me if his projections came out."

Quicktime movie link of decreasing sea ice


NOAA (National Oceanic and Atmospheric Administration) climate links