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Another False Alarm Debunked: Global Warming Wilts Malaria

Back in 2001, the University of Florida wrote one of those “science by press release” thingy’s in Eurekalert where theyspeculated that global warming would increase ranges, and thus the range of mosquito borne disease.

The next year, NPR jumped into the fray with Is Global Warming Nurturing Parasites?

In 2006 it was Warming Trend May Contribute To Malaria’s Rise in Science Daily

In 2009 Gore gets bitten again by another factual blunder getting all worked up about mosquitoes in Nairobi.

Joltin Joe Romm and NYT’s Andrew Revkin agreed last year that:

The climate blogger Joe Romm and I agree (breaking news): Scientific research and assessments examining the link between human-driven climate change and malaria exposure have, for the most part, accurately gauged and conveyed the nature of the risk that warming could swell the ranks of people afflicted with this awful mosquito-borne disease.

Also in 2010, Indur Goklany did a WUWT guest post Smacking Down Malaria Misconceptions as well as this guest post from Dr. Pat Michaels where clearly the malaria data just doesn’t add up in Peer reviewed whack a mozzie.

I’m happy to report both Romm and Revkin are wronger than wrong, and the whole AGW to malaria link has just been shot down, in Nature no less, by a Penn State study. It may also be time to revist this WUWT post: Mann’s 1.8 million Malaria grant – “where do we ask for a refund’? since he didn’t contribute to this new study.

Here’s excerpts from the story in Nature:

Global warming wilts malaria

Transmission of infectious parasites slows with rising temperatures, researchers find.

by Zoë Corbyn

A common assumption is that rising global temperatures will increase the spread of malaria — the deadly mosquito-borne disease that affects millions of people worldwide. But a study out today in Biology Letters finds that warmer temperatures seem to slow transmission of malaria-causing parasites, by reducing their infectiousness.

The study was done with rodent malaria, but the researchers, at Pennsylvania State University in University Park, expect the pattern to apply to human malaria and possibly to other mosquito-borne diseases such as dengue fever and West Nile virus.

Studies predicting that warmer climates will increase malaria infections commonly assume that the disease-causing parasites will develop faster and that the ability of the mosquito to acquire, maintain and transmit the pathogen will remain constant. They conclude that as temperature rises, mosquitoes become infectious quicker and therefore malaria transmission increases.

But the latest study shows that temperature has a more complex effect. As temperature rises, parasites do develop faster, but fewer of them become infectious.

“It is a trade-off between parasite development and parasite survival,” says Krijn Paaijmans, an entomologist and study author. “And if you don’t factor this in I think you come to the wrong conclusions.”

To tease out the factors involved, Paaijmans and his colleagues incubated mosquitoes infected with Plasmodium yoelii, which causes rodent malaria, at 20, 22, 24 and 26 degrees Celsius for 5–14 days. The researchers then examined the salivary glands of the mosquitoes — where the parasite travels when it is mature — and found that the parasite developed more quickly in warmer temperatures. But they also found fewer sporozoites — the infectious form of the parasite — indicating that the mosquitoes were less infectious at higher temperatures.

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Full story here

Will Romm finally shut up about mosquitoes and malaria now? Will Revkin write a story correcting his previous ones? Will Mike Mann give back the 1.8 million dollars?