PARIS-There is a "catastrophic" gap between national pledges to reduce greenhouse gas emissions and the actions needed to cap global warming below two degrees Celsius, the UN's environment chief warned Tuesday, days ahead of global climate talks in Bonn.

Even if fulfilled, these pledges - inscribed along with the 2 C target in the 2015 Paris climate pact - would see the world heat up 3 C (5.6 F), unleashing deadly heatwaves, superstorms and rising seas, UN Environment said in its annual Emissions Gap report, the bleakest ever.

Record-setting extreme weather in 2017 - including monsoon flooding, raging fires and deadly hurricanes - likely bears the fingerprint of global warming, it noted.

"One year after the Paris Agreement entered into force, we still find ourselves in a situation where we are not doing nearly enough to save hundreds of millions of people from a miserable future," said Eric Solheim, head of the UN agency.

"Governments, the private sector and civil society must bridge this catastrophic climate gap."

Compiled by more than 200 climate scientists and experts, the annual, 100-page analysis tracks progress toward the Paris goal of checking the rise in global temperatures at "well below" 2 C.

With many poor nations already feeling the sting of a planet out of kilter with only one degree of warming, the treaty also vowed to explore the feasibility of holding the line at 1.5 C.

Current commitments for slashing pollution take us only a third of the way toward the 2 C target, and would eat up 80 percent of humanity's "carbon budget" - the amount of CO2 we can spew into the atmosphere without crossing that threshold - by 2030, the report said.

It doesn't help that the United States, the world's second largest emitter, has abandoned its greenhouse gas goals under Donald Trump.

"Momentum is clearly faltering," said Edgar Gutierrez-Espeleta, Costa Rica's environment minister and president of the current UN Environment Assembly.

"We face a stark choice: up our ambition, or suffer the consequences."

If the gap is not closed by 2030, the report said, "it is extremely unlikely that the goal of holding global warming to well below 2 C can still be reached."

To stay on the 2 C track, humanity must cut its emissions to about 42 billion tonnes of CO2 or its equivalent by 2030 from last year's 52 billion tonnes.

Extreme weather caused some $129 billion (111 billion euros) in economic losses last year, said a report Tuesday that warned the bill will keep climbing as climate change boosts droughts, storms and floods.

There was a 46-percent increase in weather disasters from 2010 to 2016, with 797 "extreme" events recorded last year, according to research published in The Lancet medical journal.

These "resulted in $129 billion in overall economic losses" - a figure roughly matching the budget of Finland.

Losses were counted as damage to physical assets and did not include the "economic value" of deaths, injury or disease caused by extreme events.

An observed increase in weather disasters in recent years, the report said, cannot yet be unequivocally be attribute to climate change.

But the evidence "might plausibly be interpreted as showing how climate change is changing the frequency and severity of these events", the authors wrote.

Climate scientists are loath to blame any particular weather event on global warming - a phenomenon that needs to be monitored over decades.

But looking to the future, the authors are under no illusions that climate change will fuel the "frequency and severity" of tropical storms, droughts and flooding around the world.

The finances of poor countries are disproportionately hard hit, said the report compiled by experts from 24 academic institutions and inter-governmental bodies including the World Health Organization and World Meteorological Organization.

Their losses from freak weather events were more than three times higher in 2016 than in 2010, and as a proportion of GDP, much greater than in rich nations.

In high-income countries, about half of economic losses were insured, compared to less than one percent in poor nations.

The researchers calculated that rising temperatures caused a loss of about 5.3 percent in labour productivity in outdoor workers since 2000.

Over the same period, the number of vulnerable people exposed to heatwaves - putting them at risk of heatstroke, heart failure or dehydration - increased by about 125 million.

The rising mercury also caused a near 10-percent rise since 1950 in the disease-spreading "vectoral capacity" of a mosquito bearing the potentially deadly dengue virus.

"Climate change is expected to have an impact on crop production, with a one-degree-Celsius rise in temperatures associated with a six-percent decline in global wheat yields and a 10-percent decrease in rice grain yields," said a statement in The Lancet, warning of growing hunger.

The world's nations have pledged to limit average global warming caused by humankind's emission of fossil fuel gases, to two degrees Celsius (3.6 degrees Fahrenheit) from pre-Industrial Revolution levels.

We have already reached about 1 C.