The earth's atmosphere has warmed more slowly over the last
decade or so than in previous years - and a big question in climate
science right now is why.
A new paper links the so-called hiatus to natural changes in the
climate, saying it's all down to what's going on in the tropical
Pacific Ocean. But we should expect faster warming to make a
comeback, the authors warn.
greenhouse gases are driving up
global temperature. But data on land and from the surface of
the ocean in the last decade and a half show surface temperatures
have risen somewhat
slower than expected.
According to a new paper in Nature, understanding natural
changes in the Pacific Ocean is key to finding out what's causing
the "hiatus" and how long it's likely to stick around.
Pause for thought
When scientists talk about
what's causing the slowdown in surface temperature rise, a
couple of explanations usually come up. As the authors explain in
the new paper:
"Two schools of thought exist regarding
the cause of this hiatus in global warming: one suggests a slowdown
in radiative forcing ... and the other considers the hiatus to be
part of natural variability."
When volcanoes erupt they spit reflective particles into the
atmosphere. One suggestion is that an increase in these particles
together with a dip in the amount of solar energy reaching earth
could be contributing to less-than-expected warming. That's what's
meant by a change in radiative forcing.
But the new paper sits squarely in the second camp, saying the
"hiatus" is part of natural climate variability. It's all to do
with sea surface temperatures in the tropical Pacific Ocean cycling
between warm and cool phases, the paper says.