Abrupt climate change possible in coming years

EarthSky spoke with Richard Alley, a Penn State geologist and winner of a 2011 Heinz Award for his work on abrupt climate change. For the past several decades, he’s been studying ice cores – samples from the accumulation of snow and ice laid down over thousands of years in Greenland and Antarctica.

Alley did ground-breaking work in science when he helped extract a two-mile-long ice core from Greenland in the early 1990s, which shows that Earth’s climate changed abruptly in the past. With more of the greenhouse gas CO2 added each year to Earth’s atmosphere, Dr. Alley is worried that abrupt climate change could happen again. He said:

What we expect is that the world will behave itself. As we turn up CO2, the world will get warmer – but we’ll sort of know what’s coming. And we’ll be able to make wise decisions in time to slow down the rise of CO2 and stop it, or whether to adapt to the changes to come. What we’re a little worried about is that we do know from ice cores and other records that occasionally the climate is not well-behaved.

He gave us an example of what he means. Today, climate scientists predict that temperatures will rise a few degrees Fahrenheit in the next hundred years. Ice cores from Greenland show that – around 11,500 years ago – average temperatures in Greenland increased by about 15 degrees Fahrenheit, over the course of 10 years or so. Alley said this abrupt change was prompted – at least partially – by melting polar ice, which altered ocean circulation and weather patterns. As today’s climate warms, ice is again melting near Earth’s poles. Alley said:

So a lot of us are working really hard to get the fundamental physics of how these giant two-mile thick piles of ice flow, how they grow and melt, and how they might behave in the future.

EarthSky asked Alley what abrupt climate change would look like if it happened today:

Worst case scenario would be something like changing ocean circulation in a way that made it dry in the monsoon belts in places where people are expecting the rain to water their crops. We know these abrupt [climate] changes in the north Atlantic were accompanied by drought in monsoonal regions, so if we were to trigger something in the North Atlantic, it might, in turn, trigger changes in the monsoon where a huge number of people need the rain.

We’re fairly confident that the Antartic and Greenland ice sheets will stay where they are for at least awhile, but if they were to dump ice in the ocean fairly quickly, you could have very rapid sea level rise.

Alley talked about insurance against that possibility:

Less emissions of climate dioxide, basically. The other thing you look at is trying to build society so it’s a little more resilient. If your planning to build a wall around the city to keep the flood out, maybe you build it a little higher, just in case. For an area prone to flooding or drought, you put a little bit of a cushion in the way you do things, so that if things turn out to be a little worse than we expected, we have an ability to deal with it.

He said it’s not naïve to be optimistic about Earth’s climate future.

There are immense resources out there. The amount of sunlight, wind energy, and geothermal, dwarf the amount of energy that we’re using now, and they’re available with technologies that we have, or that we can get in a fairly straightforward way. If we put our brainpower to work, what we need is supplied by the planet. We can do this. We can grow the food. We can make sure people survive. We can make sure people have something good to do. We can make a sustainable future.

Listen to the 8-minute and 90-second EarthSky interviews with Richard Alley on abrupt climate change, at top of page.