As the planet’s population struggles with fiercer heatwaves, storms and wildfires, governments face growing pressure to step up their action to curb climate change by 2020, after a flagship speech by the United Nations’ chief on Monday.

Antonio Guterres warned in New York that climate change was moving faster than humankind, and appealed for leadership from politicians, business and scientists to head off the threat.

“If we do not change course by 2020, we risk missing the point where we can avoid runaway climate change, with disastrous consequences for people and all the natural systems that sustain us,” he said in a hard-hitting address.

He confirmed he would convene a climate summit in September 2019, one year before countries are due to enhance their national pledges to cut planet-warming emissions under the Paris Agreement adopted in 2015.

Guterres said he wanted to “hear about how we are going to stop the increase in emissions by 2020”, and dramatically reduce them to reach net-zero emissions by mid-century.

The Paris accord, so far ratified by about 180 countries, set a goal of limiting the rise in average global temperatures to “well below” 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial times, while “pursuing efforts” for 1.5 degrees.

“ If we do not change course by 2020, we risk missing the point where we can avoid runaway climate change, with disastrous consequences for people and all the natural systems that sustain us. Antonio Guterres, secretary general, United Nations

Temperatures are already up by about 1 degree Celsius.

“Keeping our planet’s warming to well below 2 degrees is essential for global prosperity, people’s well-being and the security of nations,” the U.N. Secretary-General said.

Marshall Islands President Hilda C. Heine described Guterres’ remarks as “an unprecedented call to arms”.

Every world leader should come to the 2019 climate summit “ready to step up their ambition” as her Pacific island nation would do at the event, she said in a statement.

“Its success will be measured by whether it helps protect the future of the most vulnerable countries like mine,” she added.

David Waskow, international climate director at the Washington-based World Resources Institute, said governments had no time to waste in strengthening their existing national plans.

“To stave off climate change, countries need to step up their commitments by 2020,” he added in a statement.

Harjeet Singh, global lead for climate change at ActionAid International, highlighted Guterres’ comments on the need to help the poorest nations and the most vulnerable people hit “first and worst” by extreme heat, storms and floods.

“Guterres’ message sends a strong signal to rich countries that they must stop backtracking on their commitments,” Singh said.

“With every month bringing a new climate disaster, the Secretary-General’s landmark warning comes not a minute too soon.”

In his speech, the U.N. chief urged wealthy governments to fulfill pledges to provide funding to developing nations so they can adapt to climate pressures and grow their economies cleanly.

“Richer nations must … not only cut their emissions but do more to ensure that the most vulnerable can develop the necessary resilience to survive the damage these emissions are causing,” said Guterres.