[LINK] Global Warming Is Irreversible, Study Says

[Bernard Robertson-Dunn]

<brd>
If global warming is irreversible, maybe we should stop tinkering with 
irreverent/irrelevant suggestions and start looking at survival strategies.
</brd>

Global Warming Is Irreversible, Study Says
by Richard Harris
All Things Considered,
January 26, 2009

Climate change is essentially irreversible, according to a sobering new 
scientific study.

As carbon dioxide emissions continue to rise, the world will experience 
more and more long-term environmental disruption. The damage will 
persist even when, and if, emissions are brought under control, says 
study author Susan Solomon, who is among the world's top climate scientists.

"We're used to thinking about pollution problems as things that we can 
fix," Solomon says. "Smog, we just cut back and everything will be 
better later. Or haze, you know, it'll go away pretty quickly."

That's the case for some of the gases that contribute to climate change, 
such as methane and nitrous oxide. But as Solomon and colleagues suggest 
in a new study published in the Proceedings of the National Academy of 
Sciences, it is not true for the most abundant greenhouse gas: carbon 
dioxide. Turning off the carbon dioxide emissions won't stop global warming.

"People have imagined that if we stopped emitting carbon dioxide that 
the climate would go back to normal in 100 years or 200 years. What 
we're showing here is that's not right. It's essentially an irreversible 
change that will last for more than a thousand years," Solomon says.

This is because the oceans are currently soaking up a lot of the 
planet's excess heat — and a lot of the carbon dioxide put into the air. 
The carbon dioxide and heat will eventually start coming out of the 
ocean. And that will take place for many hundreds of years.

Solomon is a scientist with the National Oceanic and Atmospheric 
Administration. Her new study looked at the consequences of this 
long-term effect in terms of sea level rise and drought.

If we continue with business as usual for even a few more decades, she 
says, those emissions could be enough to create permanent dust-bowl 
conditions in the U.S. Southwest and around the Mediterranean.

"The sea level rise is a much slower thing, so it will take a long time 
to happen, but we will lock into it, based on the peak level of [carbon 
dioxide] we reach in this century," Solomon says.

The idea that changes will be irreversible has consequences for how we 
should deal with climate change. The global thermostat can't be turned 
down quickly once it's been turned up, so scientists say we need to 
proceed with more caution right now.

"These are all ... changes that are starting to happen in at least a 
minor way already," says Michael Oppenheimer of Princeton University. 
"So the question becomes, where do we stop it, when does all of this 
become dangerous?"

The answer, he says, is sooner rather than later. Scientists have been 
trying to advise politicians about finding an acceptable level of carbon 
dioxide in the atmosphere. The new study suggests that it's even more 
important to aim low. If we overshoot, the damage can't be easily 
undone. Oppenheimer feels more urgency than ever to deal with climate 
change, but he says that in the end, setting acceptable limits for 
carbon dioxide is a judgment call.

"That's really a political decision because there's more at issue than 
just the science. It's the issue of what the science says, plus what's 
feasible politically, plus what's reasonable economically to do," 
Oppenheimer says.

But despite this grim prognosis, Solomon says this is not time to 
declare the problem hopeless and give up.

"I guess if it's irreversible, to me it seems all the more reason you 
might want to do something about it," she says. "Because committing to 
something that you can't back out of seems to me like a step that you'd 
want to take even more carefully than something you thought you could 
reverse."

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Regards
brd

Bernard Robertson-Dunn
Canberra Australia
brd at iimetro.com.au