[Reader-list] Lonnie Thompson interview

[Nagraj Adve]

Lonnie Thompson is one of the foremost guys on glaciers. Interesting point
he makes on glaciers thinning from the top, including in the southwest
Himalayas.
Naga


Nature Reports Climate Change
Published online: 9 July 2009 | doi:10.1038/climate.2009.66

Interview: Lonnie Thompson

 *Glaciologist Lonnie Thompson has spent more time above 20,000 feet than
any other human being. In collecting a vast library of ice samples from
mountain peaks, he has developed a unique view of past and present-day
climate change. Anna Barnett caught up with him at the American Geophysical
Union's Chapman Conference on Abrupt Climate Change, held 15–19 June at
Thompson's own Ohio State University.*

*Why hold a conference on abrupt climate change?*
[image: Interview: Lonnie Thompson]

Glaciologist Lonnie Thompson.

© THOMAS NASH

Understanding the mechanisms of abrupt changes in our climate would be
important in any period of time. But in today's world, it's especially
important given that we've never had 6.7 billion people before, and that the
potential impacts of changes on social and economic systems could be
substantial.

*Why focus on the past?*

To understand the mechanisms of abrupt changes in the present and future,
you need to know what has occurred in the past. We're fortunate to live on a
planet that has recorded very detailed histories, often annually, of how the
climate system worked in the past. We can look at the various recorders we
have, be they ice cores or trees, and learn from them to better understand
where we are today and where we may be in the future.

*What information can you garner from glaciers?*

Glaciers are like sentinels, and they're telling us that the system is
changing. The first thing we look for in the ice is radioactivity from
thermonuclear bomb tests in 1962–1963 and 1951–1952. Back in 2006, we
drilled three cores in the southwestern Himalayas. At 6,050 metres, where
those glaciers reach their highest elevation, we found that neither of these
radioactive layers was preserved. The glaciers are being decapitated. Not
only are they retreating up the mountain slopes, but they are thinning from
the top down.

This same scenario is playing out on Mount Kilimanjaro in Africa. When we
drilled there in 2000 we found the 1951 test preserved, but not the 1962
test. We've since continued to monitor those glaciers and we know that we've
lost three metres of ice since 2000. If we had waited until this year to
drill, we would not have found the 1951 bomb horizon, because that has now
been lost.

*What does that mean for climate science?*

Once a glacier melts, the history it contained is gone forever, so there's
an urgency in trying to collect the records before they are lost.

Glaciers are like sentinels, and they're telling us that the system is
changing.

The loss of tropical glaciers is very telling because they're in such
sensitive places. Half of the surface of the planet lies between 30° N and
30° S. That's where the heat that drives the climate system is received.
It's also where 70 per cent of the 6.7 billion people on the planet live.

*What's the effect on people as these glaciers disappear?*

After this meeting, we're headed to Peru to drill new ice cores at two
sites. That country contains 75 per cent of the world's glaciers. Eighty per
cent of its population is in the desert on the west coast, and 76 per cent
of the electricity comes from hydropower, from streams that are fed by
glaciers in the Andes, all of which are retreating. Those changes are
impacting the ability to produce hydropower, to irrigate crops in the desert
and to provide municipal water supplies.

*How can we deal with such changes?*

One possibility is to build dams to capture the water and do what the
glacier does for free. You can think of a glacier as a water tower. It
accumulates water in the wet season, when 70–80 per cent of precipitation
falls, and in the dry season it melts back and keeps water flowing in the
streams. Unfortunately, people live in these river valleys — usually Quechua
Indians — as have their ancestors, and there's no way that they will want
the valleys to be flooded to construct these dams. There have been riots
already, just this past year. So even if you can come up with a solution
from afar, there can be problems when you go to implement it on a local
level.

In the twenty-first century we human beings face two major problems: how do
we get along with each other, and how do we get along with our planet? Of
course, our ability to get along with each other is probably going to be
tested as we have water shortages and other climate-related impacts on
cultures and economies around the planet. So the challenge will be how we
can change the way we go about our daily activities to make our future
sustainable.