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.

    根據研究人員稱快速變暖的氣候會改變熱帶與亞熱帶地區的農作物產量，到本世紀末全球變暖有可能導致嚴重的食物短缺。并且最壞的事情在于最窮的人生活在熱帶與亞熱帶地區。根據研究人員的報告，到2100年在熱帶與亞熱帶地區最低種植季節的溫度超過有史以來的記錄溫度，有超過90%的可能性。David Battisti，華盛頓大學的大氣科學教授稱“單獨由于溫度的原因，全球食物生產的壓力是巨大的，這還不考慮更高溫度導致水分供應的壓力”。

    “對我們來說，由于根據溫度來確定方向，并且發展能夠抵抗更暖和的氣候的新型農作物產品會需要幾十年，在適應性的投資是個強迫的事情。
“我們已經看見歷史最壞的情況，并且如果沒有某種適應性的話，未來會變得更壞，”他補充道。
在研究期間，研究人員結合直接的觀察與助于獲得2007年的諾貝爾獎的23個全球氣候模型，并用這些數據作為過濾器，審視歷史上的嚴重食物短缺情況。

    他們斷言這樣的情況有可能變得更普通。.

    那些包括2003 年法國與1972年烏克蘭嚴重的情形。 在烏克蘭的那種情況下，近似記錄的熱波減少小麥產量，并且影響全球隨后兩年的谷物市場。
科學家斷言嚴重的氣候問題不僅限于熱帶地區。

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

    在熱帶地區，較高的溫度必定能導致主要農作物，玉米，大米的產量減少20-40%。而升高的溫度有可能對土壤水分導致嚴重的破壞，進而進一步減少產量。

    “我們必須從整體上重新考慮農業系統，不僅考慮新的變化，還要意識到許多人會離開農業，甚至離開他們現在的居住地”， Naylor說。

    在赤道地區的氣候變化導致溫度的升高小于較高緯度的地區，但是由于今天在熱帶地區的平均溫度比中緯度地區高的多，升高的溫度對熱帶地區的農作物產量造成嚴重的影響。

    研究結果出現在科學雜志上。