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John Kerry, the US special presidential envoy for climate, has reacted to the IPCC report, saying the "world requires real action".

"The impacts of the climate crisis, from extreme heat to wildfires, to intense rainfall and flooding, will only continue to intensify unless we choose another course for ourselves and generations to come," he said.

"All major economies must commit to aggressive climate action during this critical decade."

Former US vice-president Al Gore, a climate campaigner, also warned that governments need to take urgent action.

"Scientists have been sounding the alarm on the climate crisis for decades, and for decades we have hit the 'snooze' button, delaying action and turning a blind eye to its increasingly devastating impacts," he said.

"Now is the time for world leaders to finally wake up and take action. We cannot wait any longer."

Image source, WastelandRebel

In the wake of the IPCC report, climate experts have been warning that governments need to take urgent action to bring down global greenhouse gas emissions.

These policy changes are the most crucial aspect of the fight against climate change.

But on an everyday level, is there anything we as individuals can do to live a greener life?

Our colleagues from BBC's Radio 1 Newsbeat have spoken to sustainable bloggers about how they live zero-waste and reduce their impact on the planet.

Humanity can still prevent "runaway climate change" if nations implement carbon net zero policies, the EU's climate policy chief has said.

In a tweet, Frans Timmermans said the new report demonstrated the "immense urgency" of taking action and that countries should "act decisively now and all act together".

Earlier we heard from UK Prime Minister Boris Johnson, who said coal needed to be consigned to history to limit global warning. We have more on his comments.

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Greenhouse gases are substances in the Earth's atmosphere that trap energy from the Sun that would otherwise be released into space.

Some examples of greenhouse gases are carbon dioxide, nitrous oxide and methane.

To explain in a bit more detail - about 70% of the Sun's energy that reaches the Earth passes through the atmosphere to the surface of the planet, and is absorbed by the land, oceans and atmosphere.

This heat then radiates back up as infrared light. Some of this is released into space, but most of it gets absorbed by greenhouse gases in the atmosphere and is then redirected back towards Earth, causing the planet to warm.

This is known as the greenhouse effect.

The concentration of greenhouse gases in the Earth's atmosphere has been at around the same level for about 800,000 years. However, it has roughly doubled in the last century.

Prof Chris Hilson, from the University of Reading, England:

Prof Dave Reay, from the University of Edinburgh, Scotland:

Prof Tim Palmer, from the University of Oxford, England:

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Animals and their habitats are often destroyed in extreme weather events.

Australia's bushfires at the end of 2019 and beginning of 2020, for example, are believed to have killed or harmed about three billion animals.

And melting sea ice means that animals like polar bears are at risk of losing their habitats.

A warming planet threatens plants, too. According to one study last year, as many as 40% of the planet's plants are at risk of extinction because of climate change.

Responding to today's report, Inger Andersen, executive director of the United Nations Environment Programme, said experts had been warning for more than three decades of the consequences of a warming planet.

"The world listened but it didn't act strongly enough, and as a result, climate change is a problem that is here, now. Nobody is safe, and it's getting worse faster. We must treat climate change as an immediate threat."

She said it was within humanity's power to make the changes needed, but there was no time to waste.

"We can't undo the mistakes of the past, but this generation of political and business leaders, this generation of conscious citizens can make things right. This generation can make the systemic changes that will stop the planet warming, help everyone adapt to the new conditions, and create a world of peace, prosperity and equity," she said.

"Climate change is here, now. But we are also here now. And if we don't act, who will?"

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A drought happens when there's a prolonged period of excessively dry weather with potentially deadly consequences, such as water shortages and crop failure.

In June, for example, several key reservoirs in the US dropped to record low levels, threatening water supply for nearby cities and towns.

Not all droughts are due to climate change. However, excess heat in the atmosphere is drawing more moisture out of the earth, and this is making droughts worse.

The IPCC report's authors paint a sobering picture of an overheating world slipping deeper into crisis. Here are some of their individual comments.

Prof Ed Hawkins, from the University of Reading, England:

Prof Malte Meinshausen, from the University of Melbourne in Australia:

Dr Friederike Otto, from the University of Oxford:

Prof Piers Forster, from the University of Leeds, England:

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A number of governments are now committing to combating human-induced climate change.

In November, leaders from 196 countries will meet in Glasgow for the COP26 with the aim of agreeing on action to limit climate change and its effects.

They will also discuss whether enough has been achieved since the landmark Paris climate agreement in 2015.

And individual states and blocs have been proposing changes themselves.

Last month, for example, the EU unveiled sweeping climate proposals that included a tax of jet fuel, and an effective ban on the sale of petrol- and diesel-powered cars within 20 years.

However, these now face years of negotiations, and were criticised by climate campaigners as not going far enough.

Greenpeace's EU director Jorgo Riss said at the time the targets were "too low", adding: "Celebrating these policies is like a high-jumper claiming a medal for running under the bar".

And Greta Thunberg said the EU should "tear up" the proposals.

After stark warnings from the IPCC about climate change, UK Prime Minister Boris Johnson has called for urgent global action to cut emissions.

The UK is hosting COP26, a key climate summit, in Glasgow in November.

Johnson said the IPCC report "makes for sobering reading", and that he hoped the report would be a "wake-up call for the world to take action now" ahead of the summit.

"We know what must be done to limit global warming - consign coal to history and shift to clean energy sources, protect nature and provide climate finance for countries on the frontline," he said.

Image source, Getty Images

Although sea ice is mostly in the Arctic and Antarctic, when it melts it has a knock-on effect on the entire planet.

This is because the bright surface of the ice reflects sunlight back into the atmosphere, and out into space - keeping the polar regions much cooler than the equator.

But as the ice gradually melts, there are fewer bright surfaces to reflect this sunlight, meaning that more of the heat is absorbed at the surface and the temperature of the oceans rise.

The warmed ocean then melts the ice further, triggering a continuous cycle of warming and melting. This also disrupts the normal circulation of the ocean, which affects the rest of the world's climate too.

Sea levels are rising because of warming in the polar regions, which is both melting sea ice and causing thermal expansion - where the water physically expands as sea temperatures rise.

This is a problem because if sea levels keep rising as rapidly as they are, eventually coastal regions - and possibly entire islands - will be flooded or underwater.

Some of the land that would be lost is important for food growing, such as the delta of the Nile river.

And millions of people could be displaced. One local council in North Wales has already got a plan in place to evacuate all of the residents of its coastal village within the next 25 years, or sooner if necessary.

• Temperatures will reach 1.5C above 1850-1900 levels by 2040 under all emissions scenarios
• The Arctic is likely to be practically ice-free in September at least once before 2050 in all scenarios assessed
• There will be an increasing occurrence of some extreme events "unprecedented in the historical record" even at warming of 1.5C
• Extreme sea level events that occurred once a century in the recent past are projected to occur at least annually at more than half of tidal gauge locations by 2100
• There will be likely increases in fire weather in many regions

• Global surface temperature was 1.09C higher in the decade between 2011-2020 than between 1850-1900.
• The past five years have been the hottest on record since 1850
• The recent rate of sea level rise has nearly tripled compared with 1901-1971
• Human influence is "very likely" (90%) the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea-ice
• It is "virtually certain" that hot extremes including heatwaves have become more frequent and more intense since the 1950s, while cold events have become less frequent and less severe

Humanity's damaging impact on the climate is a "statement of fact", say UN scientists in a landmark study.

The report says that ongoing emissions of warming gases could also see a key temperature limit broken in just over a decade.

The authors also show that a rise in sea levels approaching 2m by the end of this century "cannot be ruled out".

But there is new hope that deep cuts in emissions of greenhouse gases could stabilise rising temperatures.

This sober assessment from the Intergovernmental Panel on Climate Change (IPCC) features in a 42-page document known as the Summary for Policymakers.

"Today's IPCC Working Group 1 Report is a code red for humanity," said UN Secretary-General, António Guterres.

"If we combine forces now, we can avert climate catastrophe. But, as today's report makes clear, there is no time for delay and no room for excuses. I count on government leaders and all stakeholders to ensure COP26 is a success."

We have more on what the reports says here, and stay with us for analysis from our correspondents and experts.

Christiana Figueres, who ran the UN treaty that enabled the landmark 2015 Paris Agreement, has told us a bit about what's in the report that will be released in just a few minutes.

She added that with a number of recent extreme weather events all happening within a short space of time, the situation is now at crisis point.

Navin Singh Khadka
Environment correspondent

Officials and experts have warned that low-income nations are struggling to protect themselves against climate change.

Organisations representing 90 countries say that their plans to prevent damage can't keep up with the pace of climate-induced disasters, which are intensifying and happening more regularly.

The UN says the number of developing countries with climate adaptation plans has increased. But it stresses that there's limited evidence these plans have reduced any risks.

"We need to adapt our plans to the worsening climate crisis. Our existing plans are not enough to protect our people," Sonam Wangdi, chair of the UN's Least Developed Countries (LDC) Group on climate change, said.

The UN Framework Convention on Climate Change says more than 80% of developing countries have begun formulating and implementing their national adaptation plans.

But a study by the International Institute for Environment and Development (IIED), published last month, suggests that the 46 of the world's least-developed countries don't have the financial means to "climate proof" themselves.

After a string of extreme weather disasters this year, scientists recently told us that they hadn't been able to accurately predict how quickly and severely these would happen.

This, they said, was because they lack the tools to do so.

Former Met Office chief scientist Prof Dame Julia Slingo said the climate computer models currently used "are just not good enough".

Oxford Prof Tim Palmer said:

Computers are fundamental to weather and climate change forecasting, and computing will underpin the report from the IPCC today.

We have more on this here.

Image source, Getty Images

Because of human-induced climate change, extreme weather events are becoming both more severe and more frequent.

In China's central Henan province, for example, more than 300 people were killed and almost 13 million others affected by floods that engulfed the region at the end of July.

And just a week earlier, western Europe saw its worst flooding in decades. About 120 people died after heavy rainfall hit Germany and Belgium, while the Netherlands, Luxembourg and Switzerland were also badly affected.

This week, hundreds of people have been evacuated from their homes near the Greek capital Athens because of wildfires. The city has been left cloaked in acrid smoke, and firefighters have been deployed from across Europe to help.