The earth is now hotter than at any time in recorded human history, according to worldwide research published by the Royal Swedish Academy of Science.
The research is a vital piece of evidence in establishing that pollution is heating up the planet, and that the warming that has been taking place over the last two decades is not merely a natural fluctuation of the Earth's climate as some global warming sceptics have claimed.
Last night Oxfam issued an urgent appeal for international aid as a third year of drought threatens India, Pakistan and Afghanistan. Crops are failing and livestock dying across southern Asia, says the charity, putting tens of millions of lives at risk. Drought has also hit the American Midwest, which produces grain for more than 100 countries.
Despite the increasing growing evidence of global warming, many scientists have believed up to now that the earth was hotter in the early Middle Ages, when vines grew as far north as York. Some scientists have argued, as a result, that nothing out of the ordinary is happening to the climate now.
The new research - carried out at Texas A&M University and published by the Royal Academy in its magazine, Ambio - has examined 15 different records of past climates from all round the world. The evidence included tree rings in Colorado, ice cores from Tibet, old English shipping records, ancient Chinese writings and mud from the bottom of the Sargasso Sea.
These show, say the researchers - Professor Thomas Crowley and Thomas Lowery - that worldwide there were only three, relatively short, warm periods in the early Middle Ages: 1010-1040, 1070-1105 and 1155-1190. For most of the rest of that period, the globe was relatively cool.
Even more important, though, conditions varied from place to place, and the average global temperature during even the hottest of these periods seems to have been no higher than it was in the 1950s, suggesting that the present rise is indeed unique.
A fresh series of natural disasters, increasingly attributed to the climate change, is creating havoc around the world. After a winter of record floods in Mozambique, Venezuela, Vietnam and the Indian state of Orissa, the new threat is drought.
Orissa - together with the states of Maharashtra, Gujarat and Rajasthan - has been hit by India's worst drought in a century. Famine has returned to the Horn of Africa after rains have failed for four years running. And, in some ways most ominous of all, the grain-producing states of the US Midwest are also facing disaster: the national weather service has issued a federal drought warning in spring, for the first time ever.
The United States has also announced that last winter was its warmest on record.
* Brighton was left with just three hotel beds last night as people headed to the coast to take advantage of the hot weather. At the end of the wettest April since records began, nearly 90,000 beds in the East Sussex resort were taken up by visitors making the most of the end of two weeks of almost constant rain.
Brighton tourist information centre reported an "exceptionally busy" day at the popular south coast resort, adding: "It is a very hot day down here and the seafront has been thriving."