Alarm call

It happened fast. In New York City, phones lit up warning people to get to high ground. For many, it was too late. On Wednesday night, Tropical Storm IdaWhen Hurricane Ida made landfall on August 29, it was the fifth-largest hurricane in US history. On land, it weakened and became a tropical storm. drenched the city in a record-breaking downpour. Streets became rivers, rain flooded basement flats and gushed into the subway systemDramatic videos show flooding in New York's underground public transport network. "The subway system is not a submarine," the head official said when the network was forced to close.. Across the region, at least 40 people were killed.

"The climate crisis is here," said President Biden, declaring a state of emergency. Bill de Blasio called it "the biggest wake-up call" for the dangers of global warming. Tornados flattened homes in neighbouring New Jersey, where standing in the ruins, the state's governor Phil Murphy said: "The world is changing."

It has been a summer of extreme weather. In June, a heat domeHot air trapped and forced down by atmospheric pressure. Unable to rise and cool, the air gets hotter and hotter. cooked the Pacific northwest. The heatwave ignited hundreds of wildfiresAn uncontrolled fire that burns in a forest, grassland, or other sparsely populated area. Wildfires are becoming more common with global warming.. They burned for weeks, sending smoke clouds across the Atlantic to Europe.

In July, a year's worth of rain fell on the Chinese city of Zhengzhou. In Belgium and Germany, streets were "engulfed" and homes "swallowed" by catastrophic floods. Fires blazed across southern Europe, where Greece evacuated its second-largest island and called for international assistance.

Scientists are usually careful not to blame local weather on climate change. So a UN reportThe scientific report by the Intergovernmental Panel on Climate Change (IPCC) warned that climate change was becoming inevitable and irreversible. made headlines when it said it is now an "established fact" that human-caused global warming has led to a surge in deadly weather events.

The 1.2C increase in global temperatures means there will be more megadroughts and wildfires, the report confirmed. But there will also be stronger hurricanes and worse floods, because warmer air holds more energy and moisture. A recent study showed that storms are causing 50% more rainfall than 70 years ago.

According to the World Meteorological OrganisationThe UN agency responsible for climate science. Since 1970, two million people have been killed by extreme weather events, the WMO reports. there are five times more extreme weather events than fifty years ago. The conclusion, says climatologist Michael Mann, is inescapable. "We have zero years left to avoid dangerous climate change, because it's here."

The UN has declared "code red for humanity" and is calling for "immediate, rapid and large-scale" cuts in greenhouse gases. China and the US are the world's biggest polluters, responsible for 42% of the world's carbon footprintThe total amount of greenhouse gases (including carbon dioxide and methane) that are generated by our actions. China is the top emitter with 28% of the world's total emissions. The US is second with 14%.. Campaigners hope this year's fires and floods will push them to act faster.

But talks between the two superpowers are "deadlocked". Last week, the US accused China of moving too slowly whilst China said "the ball is in the US court". They will need to agree on a way forward before November, when the world's leaders meet for the next major UN climate change conferenceAlso known as COP26, it will be the most significant meeting since the Paris Agreement in 2015, when world leaders agreed to reach net-zero emissions by the second half of this century..

With New York underwater, Biden says "we need to act." But is the American public ready? In one poll, 51% believe there will need to be "major" lifestyle changes to halt climate change. It's a majority, but only just.

Is this the summer we finally wake up?

Some say no, we are sleepwalking into climate chaos. The news is terrifying, but it is not going to change people's behaviour. We are motivated by hope not fear. When confronted by a scary and difficult problem like climate change, we bury our heads and try to ignore it. If we really want to wake up, we need simple and positive steps that make us feel optimistic about the future.

Others say yes, climate change is now impossible to ignore. For many people it was a problem happening elsewhere, but this summer it came to the richest and most powerful countries on the planet. Politicians could delay difficult decisions, but now homes and lives depend on taking action now. It must become the top priority for voters and governments and that should be a reason to be hopeful.