While Mr Trump, who has long denied the existence of man made climate change, had promised to withdraw the US from the 2015 deal, the formal process only got underway when Mike Pompeo said he had submitted a notice to the United Nations.

The notice, filed on Monday and which claimed the 2015 deal signed by 200 countries placed an “unfair economic burden” on the US economy, does not become official for one year.

“Today we begin the formal process of withdrawing from the Paris Agreement,” the secretary of state said on Twitter.

“The US is proud of our record as a world leader in reducing all emissions, fostering resilience, growing our economy, and ensuring energy for our citizens. Ours is a realistic and pragmatic model.”

Finding food on the front line of climate change Show all 17 1 /17 Finding food on the front line of climate change Finding food on the front line of climate change Balkisa Zakow, 25, with her twins Hassan and Ousseni, Tombokiery village, Niger At nine months’ pregnant with twins Balkisa Zakow, 25, feared she wouldn’t have the energy to give birth. A devastating drought made Balkisa’s harvests fail, made food prices soar, and then forced her family apart. Her husband migrated in search of work to earn money to provide for his young family, leaving her heavily pregnant and alone. “Sometimes if my husband had money he sent it to me so I could eat. Sometimes the money just doesn’t come,” she said. “I was worried I wouldn’t have the energy to give birth.” But seven-month-old twins Hassan and Ousseni are lucky, they were born the night after Red Cross support came to Tombokiery village, Niger. The Niger Red Cross provided the family with a small cash grant. “A Niger Red Cross volunteer told me to go first because she saw how exhausted I was. I used the money to buy food, then I went back home to sleep feeling relieved. Before sunrise I had given birth to my twins.” Yuki Sugiura/British Red Cross Finding food on the front line of climate change Aissa Garba, 65, gazes out of the window of her home in Tombokiery village, southern Niger Last year’s drought made Aissa’s crop fail, leaving the family with nothing to eat. In the Sahel rainfall has become erratic and wet seasons that people rely on are shrinking. The Sahel has one of the driest climates in the world, people who live here have always been incredibly resilient, are now having to adapt and survive to ever harsher conditions. The region is almost one degree hotter than in 1970 and could rise by several degrees by the end of the century. Record hot spells, desertification, loss of crops and increasingly unpredictable weather patterns are reducing people’s ability to feed themselves. Mothers are forced to eat just one meal a day so that their children can eat. Yuki Sugiura/British Red Cross Finding food on the front line of climate change Herbs dry in the entrance to Aissa’s home “When we had enough we ate three times per day, but during the shortage we only had one meal a day. The children were always following us, crying because of their hunger but we had nothing to feed them,” said Aissa. “But the Niger Red Cross brought us a cash grant. We bought millet and some rice, and with that we chased the hunger away.” Yuki Sugiura/British Red Cross Finding food on the front line of climate change Rabi Chibkao, 56, and her granddaughter Aicka Danyabou, six months, at a Red Cross nutrition centre in the village of Kiéché, southern Niger Six-month-old Aicka is struggling to gain weight. It’s been a month since her mother died and her grandmother Rabi has brought her to the Red Cross nutrition centre for help. The centre provides support to mothers and babies, weighing infants and measuring their upper arms for signs of malnutrition. The pair are two in a long queue waiting for help but a shortage of the nutrition supplement plumpy nut means that Aicka is still not at a healthy weight. Rabi said: “I had been feeding her cassava flour but I noticed didn’t help her much. When she has plumpy nut it helps a lot but sometimes there isn’t any. It has made my life very hard to bear. You can’t take care of a child properly if your own life is not good.” Yuki Sugiura/British Red Cross Finding food on the front line of climate change Ingredients for a Kuwo porridge with cassava Ingredients for a Kuwo porridge with cassava, which are given to families of malnourished children visiting the Red Cross nutrition centre. Yuki Sugiura/British Red Cross Finding food on the front line of climate change Ai Naliguido, 40, and her son Aboul Aziz, four, in their village of Kiéché, southern Niger Aboul, four, is small for his age because severe malnutrition left him physically stunted. Across the Sahel 1.5 million children are acutely malnourished, one in five will die before their fifth birthday. “His body was very weak and he was so thin,” said his mother Ai Naliguido. “It was just Garri I was feeding him made with some corn-meal, or millet.” “I took him to the hospital every week and they gave him plumpy nut. I’m so relieved that he got the help he needed to get stronger. He has gotten a lot better.” She said. Niger Red Cross volunteers from the nutrition centre visit communities to show mothers how to get the most nourishment from millet flour and drought tolerant root vegetables like cassava, which helps to keep children healthy. Yuki Sugiura/British Red Cross Finding food on the front line of climate change Ali Naliguido's empty bowl Yuki Sugiura Yuki Sugiura/British Red Cross Finding food on the front line of climate change Hassi Seyni, 30, sits with her son, Mohamad Moufitaur, 15 months old – in Tombokiery village, southern Niger First the drought made the harvests fail and then food prices inflated so high even the very basics became unaffordable for Hassi Seyni and her family. Her husband, like many others, was forced to leave to find work to earn enough money to feed the family. “We got really fearful because many men fled and left the women on their own,” said Hassi. “When he (her husband) has some money he sends it to us. This is how we lived.” “With support from the Red Cross we bought some bags of millet and corn. We bought some vegetables and some condiments. When your conscience is free from problems and you get to eat. Then you can think about the future.” Yuki Sugiura/British Red Cross Finding food on the front line of climate change Hassi Seyni eats couscous with baobab leaves Yuki Sugiura Yuki Sugiura/British Red Cross Finding food on the front line of climate change Drought resistant millet and the different ways it can be used at the mill run by a women’s cooperative in the village of Gurguzu, southeast Niger Millet is a drought resistant crop. Stems are stripped by hand and the grain pounded into flour which is slowly mixed with boiling water to make two, a thick white paste which is a staple across the region. Alternatively, water can be added to the flour to make porridge. Millet is a good source of carbohydrate but eaten alone lacks the vital nutrients needed as part of a balanced diet. When it’s available sauces are added to give flavour – such as the leaves of the Baobab tree. The mill is run by a women’s cooperative group and allows the whole village to buy grain at a cheaper price than in the market, it also helps to ensure the price is less volatile in the lean season. Yuki Sugiura/British Red Cross Finding food on the front line of climate change Millet being hand stripped Yuki Sugiura Yuki Sugiura/British Red Cross Finding food on the front line of climate change Drought tolerant cassava grown at the Red Cross market garden During the lean season a shortage in food forces the prices up to unaffordable amounts for many families. The market garden helps the local community to grow their own food and helps to stabilise prices during the lean season. Yuki Sugiura/British Red Cross Finding food on the front line of climate change 34-year-old Ouma Azzika with goat she was given from the Niger Red Cross Ouma Azzika has seven children to feed. She received this goat from the Red Cross as part of a project supporting women to provide enough food to feed their families during the lean season when food is most scare. As well as providing milk, the goat can be sold at the market to earn money to buy food. Yuki Sugiura/British Red Cross Finding food on the front line of climate change An empty bowl and spoon in Tombokiery village, Niger Yuki Sugiura Yuki Sugiura/British Red Cross Finding food on the front line of climate change A child is weighed and arm measured at the Red Cross nutrition centre in the village of Kiéché, southern Niger Yuki Sugiura Yuki Sugiura/British Red Cross Finding food on the front line of climate change A traditional cooking pot used to cook tuwo in Tombokiery village, Niger Yuki Sugiura Yuki Sugiura/British Red Cross Finding food on the front line of climate change Niger Red Cross nutrition centre sign Yuki Sugiura Yuki Sugiura/British Red Cross

The 2015 deal, which sought to cut the emissions of green house gasses in order to keep the increase in global average temperature to below 2 °C, was signed off on by around 200 nations.

While campaigning for office in 2016, Mr Trump repeatedly made clear he planned to withdraw the US. Several times he said he believed climate change was a hoax, though he later said he was joking when he said it had been invented by Beijing.

The president has repeatedly raised questions about established science, even that produced by his own experts.

Last year, a report published by various US government bodies and departments warned that with “continued growth in emissions at historic rates, annual losses in some economic sectors are projected to reach hundreds of billions of dollars by the end of the century – more than the current gross domestic product of many US states”.

Asked about the report, Mr Trump said: “I don’t believe it.”

Greta Thunberg gives speech outside White House as she joins student protest against climate change

Earlier this year, Mr Trump mocked teenage climate activists Greta Thunberg, a day after the delivered a scathing speech at the UN where she accused world leaders of failing to act to confront warming.

“She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see,” he said.

In her speech the teenager had said: “People are suffering, people are dying, entire ecosystems are collapsing. We are in the beginning of a mass extinction and all you can talk about is money and fairy tales of eternal economic growth.”

Om Monday, activists criticised the president’s actions.

Nathaniel Keohane, a vice president at the Environmental Defence Fund, one of the US’s leading environmental groups, said the president was betraying the US’s allies.

“By withdrawing, the United States abandons its allies in the fight against climate change,” he said.

“It’s yet another instance of Trump acting counter to US interest in foreign policy. He’s sacrificing a stable future for our children to serve his narrow political interests.”

He added: “The truth, is the American people want action to solve climate change.”

Michael Brune, the executive director of the Sierra Club, said: ”Donald Trump is the worst president in history for our climate and our clean air and water.