Looking at Clouds from "Both Sides Now"

Physicist has head in the clouds studying global warming

Unlike glaciers, clouds respond immediately to changes in the earth's temperature

Chad Skelton, Vancouver Sun

Published: Saturday, January 26, 2008

When some people look at clouds, they see animals. Others see faces. Philip Austin sees a lot of unanswered questions.

Austin is a cloud physicist in the department of earth and ocean sciences at the University of B.C.

And since 1983, both at UBC and before that at NASA, he has been studying how clouds behave: what makes them form, what makes them disappear and how things like temperature and pollution affect their composition.

The gaps in the IPCC's predictions are the result of a number of uncertainties, such as how much the ice caps will melt and whether the world's oceans will store less CO2.

 
But the greatest unknown? Clouds.

 
"It's the single biggest uncertainty in climate modelling right now," said Austin.

 
And it's also the most important in the short term, because clouds, unlike glaciers or oceans, respond immediately to even small changes in temperature and weather patterns.

 
Clouds impact our climate in two main ways: one that cools things down and the other that warms them up.

 
The blanket of clouds near the earth's surface generally cools the Earth by reflecting sunlight back into space that would otherwise be absorbed by the oceans and converted into heat.

 
"These low clouds are very efficient at essentially being shade umbrellas," said Austin.

 
In contrast, cirrus clouds in the cold upper atmosphere -- which cover about 30 per cent of the earth's surface -- do the reverse.

 
These clouds, which are made up of ice crystals rather than water droplets, are so thin and wispy that most sunlight passes right through them.

 
But when it comes to trapping heat from below, they function almost exactly like CO2, preventing thermal radiation from escaping the earth's atmosphere.

 
"High clouds are as effective at heating the atmosphere as low clouds are at cooling it," said Austin.

 
Ironically, one of the few things that has saved us so far from bearing the full brunt of all the CO2 we've pumped into the atmosphere is, of all things, other forms of air pollution.