World leaders must "walk the walk" at the COP26 summit in Glasgow this November to avert a climate catastrophe, London Mayor Sadiq Khan told CNBC Thursday.
Speaking to CNBC's "Squawk Box Europe," Khan warned that inaction and delay would have a disastrous impact on the environment, and called on delegates attending the summit later this year to make serious changes.
"Unless there's bold action nationally and internationally, I worry about the catastrophic consequences, not just in sub-Saharan Africa, not just in countries in South Asia or the Antarctic, but in cities in America like New York, in Germany and in London, where this summer we've faced flash flooding and the consequences of heatwaves," he said.
During Khan's tenure as mayor, London has seen the introduction of an Ultra Low Emission Zone, which charges vehicles that do not meet certain emissions standards for crossing its perimeters. Next month, the ULEZ is expanding to include more roads outside the city center. He has also introduced the £22 million ($30 million) Mayor's Air Quality Fund, which aims to support projects to improve air quality in the city.
However, Khan told CNBC Thursday that regional and city leaders needed support from federal governments to take effective action on climate change.
"COP26 has got to walk the walk," Khan said, and, referring to the signing of the landmark Paris Agreement in 2015: "In Paris, the world set out what needed to be done — now we need to set out how."
He added that he did feel somewhat optimistic that Britain's Prime Minister, Boris Johnson, would take ownership of the issue ahead of COP26 in November.
"The prime minister going to the United Nations and taking a leadership role in relation to the next 40 days gives me optimism," Khan told CNBC. "I think it's really important that we as the host of COP26 show moral leadership and real leadership. That means making sure we can together provide the $100 billion required every year [to mitigate the effects of climate change], and also showing the world how we're going to walk the walk."
"We've got a target in this country to reduce our carbon emissions by 68% by 2030," he added. "We've got to show, over the course of the next few weeks, how we're going to do that, and that will hopefully influence other countries to follow suit."
Speaking at the U.N. General Assembly in New York on Wednesday, Johnson dubbed the impending COP26 summit "the turning point for humanity."
"The world is not some indestructible toy, some bouncy plastic romper room against which we can hurl ourselves to our heart's content," he told delegates. "Daily, weekly, we are doing such irreversible damage … In just 40 days' time we need the world to come to Glasgow to make the commitments necessary."
He urged fellow world leaders to pledge to achieve carbon neutrality by the middle of the century.
"But if we are to stave off these hikes in temperature we must go further and faster — we need all countries to step up and commit to very substantial reductions by 2030," Johnson said. "I passionately believe we can do it by making commitments in four areas: coal, cars, cash and trees."
However, the prime minister faced criticism from environmental group Greenpeace after giving his address.
"The Prime Minister's quite right to say we're at a turning point. The truth is that as correct as those words to world leaders are, they ring hollow when set against Johnson's failure to take decisive action to cut emissions at home," Kate Blagojevic, head of climate at Greenpeace U.K., said in a statement.
"From ending the search for new oil to finally providing proper financial support to help the public cut carbon from their homes, there really is no end of action the government can and should be doing. The problem right now is they're is failing miserably."
Under Britain's Climate Change Act, the country aims to cut emissions by 100% by 2050 relative to 1990 levels.
Part of the strategy has been the introduction of "carbon budgeting," which sees limits set on the country's emissions for five-year periods. In April, the government announced that its sixth Carbon Budget — covering 2033 to 2037 — would "set the world's most ambitious climate change target into law," aiming to reduce emissions by 78% by 2035 compared to 1990 levels.