Global warming is likely to give rise to severe food shortage by the end of this century, according to researchers, who claim that the rapidly warming climate may alter crop yields in the tropics and subtropics.

And the worst hit will be the regions where the poorest people already live that is the tropics and subtropics.

According to the researchers, there is greater than a 90 percent probability that by 2100 the lowest growing-season temperatures in the tropics and subtropics will be higher than any temperatures recorded there to date.

"The stresses on global food production from temperature alone are going to be huge, and that doesn''t take into account water supplies stressed by the higher temperatures," said David Battisti, a University of Washington atmospheric sciences professor.

"This is a compelling reason for us to invest in adaptation, because it is clear that this is the direction we are going in terms of temperature and it will take decades to develop new food crop varieties that can better withstand a warmer climate.

"We are taking the worst of what we''ve seen historically and saying that in the future it is going to be a lot worse unless there is some kind of adaptation," he added.

During the study, the researchers combined direct observations with 23 global climate models that contributed to Nobel prize-winning research in 2007 and used the data as a filter to view historic instances of severe food insecurity.

They concluded that such instances are likely to become more commonplace.

Those include severe episodes in France in 2003 and the Ukraine in 1972. In the case of the Ukraine, a near-record heat wave reduced wheat yields and contributed to disruptions in the global cereal market that lasted two years.

The serious climate issues will not be limited to the tropics, the scientists conclude.

As an example, they cite record temperatures that struck Western Europe in June, July and August of 2003, killing an estimated 52,000 people.

The summer-long heat wave in France and Italy cut wheat yields and fodder production by one-third. In France alone, temperatures were nearly 6.5 degrees Fahrenheit above the long-term mean, and the scientists say such temperatures could be normal for France by 2100.

In the tropics, the higher temperatures can be expected to cut yields of the primary food crops, maize and rice, by 20 to 40 percent, the researchers said. But rising temperatures also are likely to play havoc with soil moisture, cutting yields even further.

"We have to be rethinking agriculture systems as a whole, not only thinking about new varieties but also recognizing that many people will just move out of agriculture, and even move from the lands where they live now," Naylor said.

Temperature increases from climate change are expected to be less in equatorial regions than at higher latitudes, but because average temperatures in the tropics today are much higher than at midlatitudes, rising temperature will have a greater impact on crop yields in the tropics.

The research appears in journal Science.

根据研究人员称快速变暖的气候会改变热带与亚热带地区的农作物产量，到本世纪末全球变暖有可能导致严重的食物短缺。并且最坏的事情在于最穷的人生活在热带与亚热带地区。根据研究人员的报告，到2100年在热带与亚热带地区最低种植季节的温度超过有史以来的记录温度，有超过90%的可能性。David Battisti，华盛顿大学的大气科学教授称“单独由于温度的原因，全球食物生产的压力是巨大的，这还不考虑更高温度导致水分供应的压力”。

“对我们来说，由于根据温度来确定方向，并且发展能够抵抗更暖和的气候的新型农作物产品会需要几十年，在适应性的投资是个强迫的事情。
“我们已经看见历史最坏的情况，并且如果没有某种适应性的话，未来会变得更坏，”他补充道。
在研究期间，研究人员结合直接的观察与助于获得2007年的诺贝尔奖的23个全球气候模型，并用这些数据作为过滤器，审视历史上的严重食物短缺情况。

他们断言这样的情况有可能变得更普通。.

那些包括2003 年法国与1972年乌克兰严重的情形。 在乌克兰的那种情况下，近似记录的热波减少小麦产量，并且影响全球随后两年的谷物市场。
科学家断言严重的气候问题不仅限于热带地区。

例如，他们举例说明在西欧2003年6、7、8月的温度，杀死了大约52,000人。
在法国与意大利，夏日长热波导致小麦产量与饲料产量减少1/3。单在法国，温度将近高于长期平均温度6.5℉，并且科学家称到2100年这样的温度是正常的。

在热带地区，较高的温度必定能导致主要农作物，玉米，大米的产量减少20-40%。而升高的温度有可能对土壤水分导致严重的破坏，进而进一步减少产量。

“我们必须从整体上重新考虑农业系统，不仅考虑新的变化，还要意识到许多人会离开农业，甚至离开他们现在的居住地”， Naylor说。

在赤道地区的气候变化导致温度的升高小于较高纬度的地区，但是由于今天在热带地区的平均温度比中纬度地区高的多，升高的温度对热带地区的农作物产量造成严重的影响。

研究结果出现在科学杂志上。