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Sir David Attenborough has told world leaders at the G7 that they are facing the most important decisions in human history when it comes to climate change.

The TV presenter and wildlife expert will speak to the leaders gathered in Cornwall on Sunday as they set out plans to improve the global environment.

Climate change is one of the key issues the leaders are discussing during their three-day stay in Cornwall's Carbis Bay, but ahead of Sunday's meeting, Sir David has warned that humans could be "on the verge of destabilising the entire planet".

Sir David said: "The natural world today is greatly diminished. That is undeniable.

"Our climate is warming fast. That is beyond doubt. Our societies and nations are unequal and that is sadly plain to see.

"But the question science forces us to address specifically in 2021 is whether as a result of these intertwined facts we are on the verge of destabilising the entire planet.

"If that is so, then the decisions we make this decade - in particular the decisions made by the most economically advanced nations - are the most important in human history."

The group of seven leaders from the UK, US, Canada, Japan, France, Germany and Italy - are expected to promise to almost halve their carbon emissions by 2030 from the levels seen in each country in 2010.

China, which according to one report was responsible for 27% of the world's greenhouse gases in 2019 - the most of any country - is not part of the G7.

The US, which is a part of the G7, is the second largest producer of greenhouse gasses in the world.

President Biden says he wants America to be a global leader on fighting climate change. It comes after President Trump pulled the country out of the Paris climate agreement - a promise by countries to act on climate change - during his time in office.

Here, the UK has already hit the 30% target and has set a new aim of reducing carbon levels by 58% from what they were in 2010.

The cause of climate change?

When we talk about climate change, it means global changes in the Earth's average temperature.

Temperatures naturally go up and down over time, but scientists say temperatures are now rising faster than at many other times.

This is linked to the greenhouse effect, which describes how the Earth's atmosphere traps some of the Sun's energy.

Light from the sun passes through the atmosphere and is absorbed by the Earth's surface, warming it. Greenhouse gases, like carbon dioxide, act like a blanket, trapping heat near the surface and raising the temperature.