Passage 5 Climate Change: How Fast Is the Earth Shifting?
气候变化新标准 《时代周刊》

[00:01]There are many units by which to measure the impact of climate change:
[00:07]degrees of increasing temperature, feet of rising sea level,
[00:12]dollars needed to adapt to a warming world.
[00:15]But a group of scientists in California
[00:19]have put forth an intriguing new unit of measurement: kilometers per year.
[00:26]Writing in a paper published Wednesday in Nature,
[00:31]scientists describe what they call the velocity of climate change,
[00:37]or more specifically, the speed of Earth's shifting climatic zones.
[00:44]As global temperature rises over the next century, the scientists argue,
[00:50]Earth's habitable climatic zones will start moving too,
[00:56]generally away from the Equator and toward the poles.
[01:01]That means many species of plants and animals will also have to move in order to survive.
[01:11]Whether or not they do will depend on several factors,
[01:15]but two of the most important are how fast a species can adjust its habitat range,
[01:24]and how quickly that range is moving out from under it.
[01:29]Until now, ecologists have mostly focused on these factors as they affect individual species,
[01:39]but the new paper takes a more global view.
[01:44]By combining temperature projections on a very fine scale with global topographic maps,
[01:52]researchers have predicted change not for specific species,
[01:57]but for the climatic zones they need to keep up with.
[02:02]Indeed, because global temperature is rising now, ecosystems are already on the move.
[02:11]"Once you explain it to people, it makes intuitive sense," says co-author David Ackerly,
[02:19]a University of California, Berkeley, biologist.
[02:24]"We know what it's like to drive north to escape the heat.
[02:30]It's concrete, rather than the abstractness of rising average temperatures."
[02:36]More than intuitive, this new index could also prove very useful,
[02:43]especially to conservationists who work to keep species from extinction.
[02:50]While the average velocity of climate change may be a bit less
[02:56]than a half-kilometer per year worldwide, according to the paper,
[03:02]it can be significantly faster or slower depending on the local topography.
[03:10]In deserts and other flat areas, such as the Amazon basin,
[03:16]climatic zones will move faster, while hilly or mountainous terrain will slow things up.
[03:24]"In the Northern Hemisphere, for example,"
[03:28]explains lead author Scott Loarie, "north-facing slopes tend to be cooler
[03:35]and wetter than south-facing slopes."
[03:39]In short, opposite sides of a mountain may have different climates,
[03:45]even though they're close to each other.
[03:49]In areas with varied terrain including lots of hills, therefore,
[03:55]hospitable conditions might be available relatively nearby.