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.

    根據(jù)研究人員稱快速變暖的氣候會(huì)改變熱帶與亞熱帶地區(qū)的農(nóng)作物產(chǎn)量，到本世紀(jì)末全球變暖有可能導(dǎo)致嚴(yán)重的食物短缺。并且最壞的事情在于最窮的人生活在熱帶與亞熱帶地區(qū)。根據(jù)研究人員的報(bào)告，到2100年在熱帶與亞熱帶地區(qū)最低種植季節(jié)的溫度超過(guò)有史以來(lái)的記錄溫度，有超過(guò)90%的可能性。David Battisti，華盛頓大學(xué)的大氣科學(xué)教授稱“單獨(dú)由于溫度的原因，全球食物生產(chǎn)的壓力是巨大的，這還不考慮更高溫度導(dǎo)致水分供應(yīng)的壓力”。

    “對(duì)我們來(lái)說(shuō)，由于根據(jù)溫度來(lái)確定方向，并且發(fā)展能夠抵抗更暖和的氣候的新型農(nóng)作物產(chǎn)品會(huì)需要幾十年，在適應(yīng)性的投資是個(gè)強(qiáng)迫的事情。
“我們已經(jīng)看見(jiàn)歷史最壞的情況，并且如果沒(méi)有某種適應(yīng)性的話，未來(lái)會(huì)變得更壞，”他補(bǔ)充道。
在研究期間，研究人員結(jié)合直接的觀察與助于獲得2007年的諾貝爾獎(jiǎng)的23個(gè)全球氣候模型，并用這些數(shù)據(jù)作為過(guò)濾器，審視歷史上的嚴(yán)重食物短缺情況。

    他們斷言這樣的情況有可能變得更普通。.

    那些包括2003 年法國(guó)與1972年烏克蘭嚴(yán)重的情形。 在烏克蘭的那種情況下，近似記錄的熱波減少小麥產(chǎn)量，并且影響全球隨后兩年的谷物市場(chǎng)。
科學(xué)家斷言嚴(yán)重的氣候問(wèn)題不僅限于熱帶地區(qū)。

    例如，他們舉例說(shuō)明在西歐2003年6、7、8月的溫度，殺死了大約52,000人。
在法國(guó)與意大利，夏日長(zhǎng)熱波導(dǎo)致小麥產(chǎn)量與飼料產(chǎn)量減少1/3。單在法國(guó)，溫度將近高于長(zhǎng)期平均溫度6.5℉，并且科學(xué)家稱到2100年這樣的溫度是正常的。

    在熱帶地區(qū)，較高的溫度必定能導(dǎo)致主要農(nóng)作物，玉米，大米的產(chǎn)量減少20-40%。而升高的溫度有可能對(duì)土壤水分導(dǎo)致嚴(yán)重的破壞，進(jìn)而進(jìn)一步減少產(chǎn)量。

    “我們必須從整體上重新考慮農(nóng)業(yè)系統(tǒng)，不僅考慮新的變化，還要意識(shí)到許多人會(huì)離開(kāi)農(nóng)業(yè)，甚至離開(kāi)他們現(xiàn)在的居住地”， Naylor說(shuō)。

    在赤道地區(qū)的氣候變化導(dǎo)致溫度的升高小于較高緯度的地區(qū)，但是由于今天在熱帶地區(qū)的平均溫度比中緯度地區(qū)高的多，升高的溫度對(duì)熱帶地區(qū)的農(nóng)作物產(chǎn)量造成嚴(yán)重的影響。

    研究結(jié)果出現(xiàn)在科學(xué)雜志上。