In Donald Trump’s lengthy State of the Union speech to Congress, he spoke about the US economy, took aim at Democrats’ plans for healthcare funding, and defended gun rights, but he failed to mention perhaps the biggest issue the planet faces: the climate crisis.

The US president has had an inconsistent and contradictory record on the subject, previously dismissing it as a “Chinese hoax”, “mythical”, “non-existent” and pulling America out of the Paris agreement, though he has also described climate change as “very important”.

The glaring omission from Mr Trump’s Tuesday night speech did not escape the notice of Bernie Sanders, who along with Pete Buttigieg, is now apparently leading the race to become the Democrats’ next presidential candidate.

“As important as it is to respond to what President Trump said tonight, it is equally important to discuss what Trump refused to talk about. In the year 2020, how can a president of the United States give a State of the Union speech and not mention climate change?” Mr Sanders said to supporters following Mr Trump’s address.

The climate – long relegated to the bottom of the list of concerns – is now a major issue in American politics. Late last year, polls revealed over two thirds of US citizens now believe climate change is either a crisis or a serious problem.

This has also been bolstered by several years of extreme weather events, including terrifying wildfires in California and the damage wreaked by ever larger tropical storms.

Over 120,000 weather records were broken across the US in 2019, including for daily high and low temperatures as well as for levels of rain and snow.

Heat waves hit Alaska raising temperatures to over 30C (90F) and sparking wildfires, winter storms brought snow to Hawaii, and heavy rains brought widespread flooding to the Midwest destroying crops.

Wildfires spread across California – in pictures Show all 32 1 /32 Wildfires spread across California – in pictures Wildfires spread across California – in pictures Firefighters battle a blaze at the Salvation Army Camp in Malibu Getty Wildfires spread across California – in pictures Flames from the Camp fire burn near a home atop a ridge near Big Bend AFP/Getty Wildfires spread across California – in pictures Cathy Fallon (centre) who stayed behind to tend to her horses during the Camp Fire, embraces Shawna De Long (left) and April Smith who brought supplies for the horses Reuters Wildfires spread across California – in pictures A helicopter drops flame retardant on a wildfire in Malibu Getty Wildfires spread across California – in pictures An air tanker drops water on the fire along the Ronald Reagan Freeway in Simi Valley AP Wildfires spread across California – in pictures An abandoned car from fleeing residents of Paradise in the Pentz road area EPA Wildfires spread across California – in pictures A firefighter tackles the fire along the Ronald Reagan Freeway in Simi Valley AP Wildfires spread across California – in pictures A Jack In The Box fast food restaurant burns as the Camp fire moves through Paradise, California AFP/Getty Wildfires spread across California – in pictures Yuba and Butte County Sheriff officers label a body bag AFP/Getty Wildfires spread across California – in pictures Firefighters hose down trees on Bell Canyon Road, near Malibu AFP/Getty Wildfires spread across California – in pictures A fire burns at the Salvation Army Camp Getty Wildfires spread across California – in pictures A firefighting DC-10 makes a fire retardant drop over a wildfire in the mountains near Malibu Canyon Road AP Wildfires spread across California – in pictures A house burns in Paradise, California AFP/Getty Wildfires spread across California – in pictures Bins have melted and ballooned in the heat in Magalia, Butte County EPA Wildfires spread across California – in pictures Satellite image taken on 8 November shows plumes of smoke from the Camp Fire stretching across portions of Northern California AFP/Getty Wildfires spread across California – in pictures Firefighters battle the Camp Fire AP Wildfires spread across California – in pictures Firefighters battle the Woolsey Fire Reuters Wildfires spread across California – in pictures Deputy Coroner Justin Sponhaltz, of the Mariposa County Sheriff's Office, recovers human remains found at a home destroyed by the Camp Fire AP Wildfires spread across California – in pictures Buildings burn in Paradise, California EPA Wildfires spread across California – in pictures Local residents bring their horses to Zuma Beach and away from the Woolsey Fire in Malibu Reuters Wildfires spread across California – in pictures A used car dealership burns in Paradise, California Reuters Wildfires spread across California – in pictures Yuba and Butte County Sheriff officers inspect a burned vehicle after discovering remains nearby in Concow AFP/Getty Wildfires spread across California – in pictures Firefighters battle the flames in Thousand Oaks Reuters Wildfires spread across California – in pictures A house burns in Paradise, California AFP/Getty Wildfires spread across California – in pictures A house burns in Paradise, California AP Wildfires spread across California – in pictures Search and rescue teams work to evacuate patients from the burning Feather River Hospital in Paradise, California AFP/Getty Wildfires spread across California – in pictures Embers blow in the wind in Paradise, California AFP/Getty Wildfires spread across California – in pictures In Butte County, the sky is filled with the smoke of the Camp Fire EPA Wildfires spread across California – in pictures Firefighters at work in Thousand Oaks Reuters Wildfires spread across California – in pictures A house burns in Paradise, California AP Wildfires spread across California – in pictures The burned remains of a house and car are left after the Camp Fire in Paradise, California AFP/Getty Wildfires spread across California – in pictures A shop burns in Paradise, California AFP/Getty

Also in 2019, teenage climate activist Greta Thunberg was made Time magazine’s person of the year, lending the climate movement considerable prominence.

The accolade did not impress the US president. Mr Trump responded on Twitter: “So ridiculous. Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!”

As Mr Sanders chases the Democrat nomination, he did not miss the opportunity to hammer home the differences between himself and Mr Trump, with the climate crisis a key weapon with which to wallop the president.

He said: “How do you give a speech – a State of the Union speech – and not mention climate change when the leading scientists of the world tell us that climate change is the greatest existential threat facing humanity, and that they as scientists have actually underestimated the speed and the severity with which climate change is wreaking havoc on our country and the entire world.

“I did not hear President Trump say one word about what it means when Australia is now on fire because of severe drought. And about the unprecedented level of flooding and extreme weather disturbances that we are experiencing. And he failed to talk about how many American communities could be underwater in the next century as a result of rising sea levels.

“By ignoring and in fact exacerbating the crisis of climate change, President Trump is turning his back on the children of America and on future generations and dooming them to live on a planet increasingly unhealthy and uninhabitable.”