Climate change has unexpected effects

On the surface, global warming may seem like a pretty simple process.
Excess “greenhouse” gases trap heat in the atmosphere, making the world
warmer. But that’s not all that happens. Our climate is actually very
complex and intimately connected to life on Earth. Seemingly minor changes
can have profound repercussions.

Vol. 7 No. 14
January 25, 2006
Science Matters
by David Suzuki
Climate change has unexpected effects
On the surface, global warming may seem like a pretty simple process.
Excess “greenhouse” gases trap heat in the atmosphere, making the world
warmer. But that’s not all that happens. Our climate is actually very
complex and intimately connected to life on Earth. Seemingly minor changes
can have profound repercussions.
Consider ocean currents. Remember that big blockbuster movie a few years
ago based on the theory of rapid climate change? Well, it wasn’t exactly
rocket science, but it was based on a kernel of truth. In the movie, global
warming triggers a collapse of the “thermohaline circulation,” a system of
currents including the Gulf Stream that circulate water in the Atlantic.
Eastern North America and Western Europe depend on this circulation to
bring warmer water up from the tropics and help moderate their climates.
According to the Hollywood version, a collapse of the thermohaline
circulation would thrust New York and London into an instant ice age.
Reality is less dramatic, of course, but recent evidence has found that
this massive system can indeed be disrupted and it has happened fairly
recently. A study by NASA’s Goddard Institute for Space Studies looked at
the last event, which is thought to have occurred 8,200 years ago when an
ice dam in Canada burst, sending a massive flood of freshwater into the
Arctic Ocean. This reduced the Arctic’s salinity and slowed the
thermohaline current, dropping temperatures in Greenland by up to seven
degrees Celsius for three centuries.
Results of another study, published this fall in Nature, show that the
thermohaline current may again be weakening, this time as a result of
melting snow and glaciers due to climate change. Last year, a team of
scientists from the U.K.’s National Oceanography Centre sampled water
temperature and salinity every 50 kilometres in the Atlantic between the
Bahamas and the Canary Islands. They compared data from these samples to
data from water collected on four other trips dating back as far as 1957
and concluded that today’s current seems to be 30 per cent weaker than it
was 50 years ago. So far, air temperatures in Western Europe do not appear
to have been affected by the change.
In the tropics, however, small changes in air temperature attributed to
global warming are believed to be responsible for the widespread extinction
of amphibians. According to a recent paper published in Nature, climate
change is altering cloud cover in the mountains of Central and South
America, leading to cooler days and warmer nights. This change creates
ideal living conditions for a pathogenic fungus, which attaches itself to
amphibians, such as frogs, causing dehydration and eventually death.
The fungus has taken a real toll in the tropical Americas, where 67 per
cent of 110 species of harlequin frog in the region have died out in just
20 years. Hardest hit have been those species living at mid-elevations,
where researchers surmise conditions are optimal for growth of the fungus.
They conclude that, “climate-driven epidemics are an immediate threat to
biodiversity.”
Indeed, a changing climate has also been implicated in the increase of
nematode parasites in musk oxen and the continuing destruction of pine
forests by the mountain pine beetle. The relationship between an increase
in pathogens and a changing climate is also cause for concern in regards to
human health. A warmer world may be a sicker one for humans as well.
Climate change is not a simple process. Our atmosphere, our oceans, and all
life on the planet are interconnected. Seemingly small alterations in one
area can reverberate through the entire system, affecting the health of a
tremendous variety of species – including us.
Take the Nature Challenge and learn more at www.davidsuzuki.org.
– 30 –