Mohenjo-daro, a ruined city in what is now Pakistan that contains the last traces of a 4,000-year-old civilisation that flourished on the banks of the river Indus, today entered the modern history books after government meteorologists recorded a temperature of 53.7C (129F). Only Al 'Aziziyah, in Libya (57.8C in 1922), Death valley in California (56.7 in 1913) and Tirat Zvi in Israel (53.9 in 1942) are thought to have been hotter.

Temperatures in the nearest town, Larkana, have been only slightly lower in the last week, with 53C recorded last Wednesday. As the temperatures peaked, four people died, including a prisoner serving a life sentence for murder and an elderly woman. Dozens are said to have fainted.

The extreme heat was exacerbated by chronic power cuts which have prevented people from using air-conditioning. The electricity has cut out for eight hours each day as part of a severe load-shedding regime that has caused riots in other parts of Pakistan where cities are experiencing a severe heatwave with temperatures of between 43C and 47C.

"It's very tough," said M B Kalhoro, a local correspondent for Dawn.com, an online newspaper. "When the power is out, people just stay indoors all the time."

The blistering heat now engulfing Pakistan stretches to India where more than 1,000 people have reportedly died of heatstroke or heart attacks in the last two months. Although Europe and China have experienced cooler than average winters, record or well-above average temperatures have been recorded in Tibet and Burma this year.

Southern Europe was yesterday rapidly warming after a particularly cool winter. Thirteen provinces in southern Spain, including Andalucia, Murcia and the Canary islands, were put on "yellow alert" after meteorologists forecast temperatures rising to 38C (99F) in Cadiz, Córdoba, Jaén, Malaga and Seville.

According to the US National Oceanic and Atmospheric Association (NOAA), the national climate monitoring service that measures global temperatures by satellite, 2010 is shaping up to be one of the hottest years on record. The first four months were the hottest ever measured, with record spring temperatures in northern Africa, south Asia and Canada.

The global temperature for March was a record 13.5C (56.3F) and average ocean temperatures were also the hottest for any March since record-keeping began in 1880.

As a result of high sea surface temperatures, the Atlantic hurricane season, which officially started today is now expected to be one of the most intense in years. Last week NOAA predicted 14 to 23 named storms, including eight to 14 hurricanes, three to seven of which were likely to be "major" storms, with winds of at least 111mph. This is compared to an average six-month season of 11 named storms, six of which become hurricanes, two of them major.

On Sunday, scientists reported that Africa's Lake Tanganyika, the second deepest freshwater lake in the world, is now at its warmest in 1,500 years, threatening the fishing industry on which several million lives depend. The lake's surface waters, at 26C (78.8F), have reached temperatures that are "unprecedented since AD500," they reported in the journal Nature Geoscience.

Some scientists have suggested that the warming experienced around the world this year is strongly linked to warmer than usual currents in the Pacific Ocean, a regular phenomenon known as El Niño. Others say that it is consistent with long-term climate change.