19 June 2010

Rain Won't Go Away

Recent deadly heavy rains in the U.S., France and China may be part of a long-term trend toward heavier downpours due to climate change. (See earlier post.)

If you can't see the video, watch it on YouTube here.

Scientists from the Met Office, the UK's national weather bureau, have published research showing that the changes in rainfall patterns already attributed to climate change will persist even if global greenhouse gas emissions are controlled.

"A team led by Peili Wu used a computer model to analyse how the Earth's water cycle could react to changes in future amounts of carbon dioxide in the atmosphere. It found that once carbon dioxide levels rise to a high level, even sharp reductions fail to prevent longlasting impacts on snow and rainfall." [Source: Guardian article.]
Our results suggest that relationships between precipitation and warming may significantly underestimate precipitation changes during periods of [greenhouse gas] stabilisation or reduction. The inertia due to the accumulated heat in the ocean implies a commitment to changes long after stabilisation. This effect must be taken into account when assessing the implications of various mitigation options for flooding, water supply, food production and human health.
Their model assumed substantial increases in atmospheric CO2, up to a level of 1,000 ppm (up from today's 390 ppm and pre-industrial levels of 280 ppm) over many decades, then a rapid reduction back to 280 ppm. Because of the substantial amount of heat that would become trapped in the oceans, where it leads to increased rainfall, altered rainfall patterns would persist for a long time after CO2 levels were reduced.

This model embodies an extreme hypothesis, but it makes an important point. Just fixing greenhouse gas emissions, which seems to be politically impossible anyway, does not reverse climate changes. Get used to a very different Earth.

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