In photos: Heat wave across South East Asia, Europe

The world's hottest year on record so far was 2016, coinciding with a strong El Nino - although climate change has fuelled extreme temperatures even in years without the phenomenon. Above: A customer stands under a cooling mist spray at a street kiosk during high temperatures in central Madrid, Spain. Spring in Spain will resemble the middle of the summer this week as thermometers rise above 30 degrees Celsius (86 Fahrenheit) and some regions are forecast to hit 40 Celsius (104 Fahrenheit).

A man refreshes himself with a water hose outside a 'caseta' (tent where food and drinks are served) in the annual traditional April Fair in Seville, Spain.

The last eight years were the world's eight hottest on record - reflecting the longer-term warming trend driven by greenhouse gas emissions. Above: Young surf students dive from a pier at Carcavelos Beach, outside Lisbon.

The world could breach a new average temperature record in 2023 or 2024, fuelled by climate change and the anticipated return of the El Nino weather phenomenon, climate scientists say. Above: A woman shield herself from the sun during a heat wave in Bangkok, Thailand.

Climate models suggest that after three years of the La Nina weather pattern in the Pacific Ocean, which generally lowers global temperatures slightly, the world will experience a return to El Nino, the warmer counterpart, later this year. Above: People sit in the shade to shelter from the sun during heatwave conditions in Yangon.

During El Nino, winds blowing west along the equator slow down, and warm water is pushed east, creating warmer surface ocean temperatures. Above: A plant is photographed on a cracked earth after the water level has dropped in the Sau reservoir, about 100 km (62 miles) north of Barcelona, Spain. Drought-stricken Spain says last month was the hottest and driest April since records began in 1961.

Europe experienced its hottest summer on record in 2022, while climate change-fuelled extreme rain caused disastrous flooding in Pakistan, and in February, Antarctic sea ice levels hit a record low. Above: Workers unload blocks of ice at a wet market during a heatwave in Bangkok, Thailand.

According to experts, the world's average global temperature is now 1.2C higher than in pre-industrial times, Despite most of the world's major emitters pledging to eventually slash their net emissions to zero, global CO2 emissions last year continued to rise.