Sunday, March 7, 2010

Climate change for Hawai'i weather: maybe drier, but generally few big changes

A research team studying global impacts of climate change has found that Hawai'i will generally have few major disruptions, although weaker trades could reduce rainfall.

Much of the rest of the world may see dramatic changes in rainfall, in temperatures, in storm frequencies, but the Islands appear to be in a kind of mid-Pacific sweet spot.

That's one conclusion from a paper, Global Warming Pattern Formation: Sea Surface Temperature and Rainfall, by Shang-Ping Xie and Jian Ma of the University of Hawai'i School of Ocean and Earth Science and Technology's International Pacific Research Center, along with Clara Deser and Haiyan Teng of the National Center for Atmospheric Research, and Gabriel Vecchi and Andrew Wittenberg of the NOAA Geophysical Fluid Dynamics Laboratory.

Their paper was published in the Feb. 15, 2010, "Journal of Climate" of the American Meteorological Society. It uses a range of climate models to study potential changes in global weather patterns.

It's a complex paper, but among its conclusions:

With the anticipated changes in global temperatures over the coming half century, rainfall for Hawai'i will probably not be significantly impacted. Maybe some reduction in rain overall, maybe some local changes depending on specific geographic features like mountains and valleys.

Other studies have suggested a slight reduction in rainfall in the Islands.

Xie and co-authors do see a weakening of tradewind flow, which could result in some reduction in Hawai'i rainfall. Depending on when it occurs, it could also change the comfort levels for people living in the Islands.

The researchers find that tropical storm frequency will not change significantly in Hawaiian waters.

One of the key piece of information—and this has been a big feature of recent debate over climate change—is that while warming is occurring, it's not distributed evenly across the globe.

As an example, while Hawai'i's changes are comparatively minor, the models suggest significant increases in rainfall in the Intertropical Convergence Zone to the south of the Islands. And while our storm frequency is not anticipated to change much, the hurricanes in the Pacific south of the equator are expected to be more common, in association with significant warming of the ocean in that area.

For Samoa, the Cooks, French Polynesia and other nations in that part of the sea, that's not good news.

© Jan TenBruggencate 2010

1 comment:

Dave Smith said...

Thanks for the heads-up on the paper.

Those of us in Puna on the Big Island are hoping that the tradewinds are just weaker and don't stop flowing more often, as that means more vog coming our way.

And since many of our biggest storms are the result of moisture being brought north from the Intertropical Convergence Zone, one wonders if that means those heavy rains might end up heavier.