Many of the deadly heatwaves and hurricanes, droughts and floods this decade have borne the imprint of man-made global warming, said a series of reports Tuesday that warned of worse to come.

With one eye on the American presidential contest between climate change denier Donald Trump and Democrat Hillary Clinton, UN envoys gathered in Morocco for a second day of talks on putting the Paris Agreement into action.

Trump had vowed to "cancel" the climate rescue pact if he wins, but a series of new reports warned Tuesday of the importance of staying the course.

According to the World Meteorological Organization (WMO), the last half-decade from 2011 to 2015 was the warmest five-year stretch on record, with 2014 and 2015 the hottest years of all.

In a report issued on the sidelines of the Marrakesh gathering, it warned of "the increasingly visible human footprint on extreme weather and climate events with dangerous and costly impacts."

Climate change "has increased the risks of extreme events such as heatwaves, drought, record rainfall and damaging floods," WMO secretary general Petteri Taalas said in a statement.

In a separate report, risk analysts Germanwatch said more than half-a-million people worldwide died as a result of almost 11,000 extreme weather events from 1996 to 2015.

These caused damage upwards of three trillion dollars (2.7 trillion euros).

Four of the 10 countries hardest hit by extreme weather events in 2015 were in Africa, said Germanwatch.

Poor countries, which contributed least to the planet-warming greenhouse gases now in Earth's atmosphere, were also least prepared to deal with the fallout -- superstorms, extreme drought, heatwaves and flooding, it added.

Mozambique topped the list of nations most affected on the agency's Global Climate Risk Index, followed by Dominica, Malawi and India.

Myanmar, Ghana and Madagascar were also among the top 10.

- 'Little time to adapt' -

The Paris Agreement, the world's first universal climate pact, vows to cap global warming to under two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels, while aiming for 1.5 C.

This will be done through curbing emissions of manmade greenhouse gases, mainly from burning coal, oil and gas for heat and energy.

The UN talks in Marrakesh will negotiate rules for implementing the accord, which entered into force last week.

Climate scientists find it difficult -- when assessing an individual extreme weather event -- to determine the proportion of blame ascribed to global warming instead of natural climate variability.

But rapidly-accumulating climate data has recently made it easier to compare what is happening to the climate to past predictions about the impacts of manmade warming.

Looking over five-year time scales helps smooth out natural year-to-year variations and reveal the role of climate change a little more clearly.

"Of 79 studies published by the Bulletin of the American Meteorological Society between 2011 and 2014, more than half found that human-induced climate change contributed to the extreme event in question," said the WMO report.

The correlation with climate change was strongest for high temperatures, according to the WMO, but less obvious for rain and snow.

Adding to the warnings, Britain's National Oceanography Centre said warming of 2 C by 2040 would see more than 90 percent of the world's coastal areas experience sea level rise of more than 20 centimetres (7.8 inches).

The Atlantic coast of North America and Norway would see as much as 40 cm.

"Coastal cities and vulnerable tropical coastal ecosystems will have very little time to adapt to the fast sea level rise these predictions show," said the paper's lead author Svetlana Jevrejeva.

In a worst-case-scenario 5 C-warmer world, 80 percent of coastlines would have sea levels rise over 1.8 metres (5.9 feet) by the end of the century.

Oceans rise partly due to water expanding as it warms, but also from the melting ice sheets of Greenland and West Antarctica.

2015 set a number of frightening climate records, the WMO noted.

Among others, it was the first year in which the average global surface temperature -- across land and sea -- was a full 1 C over the pre-industrial benchmark.