World leaders have travelled to Glasgow this week as COP26 begins, a summit seen as crucial to tackling climate change and preventing disaster which would befall the planet if global warming continued. Today COP26 president Alok Sharma warned the summit was the world's "last, best hope" to limit global warming to 1.5C by 2100.

       Speaking at the opening of COP26 today Mr Sharma said: "If we act now, and we act together, we can protect our precious planet.

       "So, let's come together in these two weeks and ensure that where Paris promised, Glasgow delivers."

       Integral to limiting warming to the 1.5C figure by 2100 is reducing carbon dioxide (CO2) emissions.

       Extra CO2 in the atmosphere increases the greenhouse effect - warming the planet by trapping thermal energy and causing warmer climates than usual.

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       Some countries have pledged to hit net zero carbon emissions in the future - while others are facing pressure to reach the target sooner.

       Figures from our World in Data show the country with the highest CO2 emissions is China, with 10,175 million tonnes in 2019.

       And overall China emitted 27 percent of the world's greenhouse gases in 2019.

       Second on the list was the United States, emitting 5,258 million tonnes in 2019, 11 percent of the globe's greenhouse gases.

       China - 10,175m - 7.1 per capita

       USA - 5,285m - 16.1 per capita

       India - 2,616m - 1.9 per capita

       Russia - 1,678m - 11.5 per capita

       Japan - 1,107m - 8.7 per capita

       Iran - 780m - 9.5 per capita

       Germany - 702m - 8.4 per capita

       Indonesia - 618m - 2.3 per capita

       South Korea - 611m - 11.9 per capita

       Saudi Arabia - 582m - 17.0 per capita

       Source - Our World in Data

       China has also been ranked as "highly insufficient" when it comes to climate action, with Russia one level worse at "critically insufficient".

       In 2015, 192 nations signed the Paris Accord which set out a global framework to avoid dangerous climate change.

       The UK has promised to hit net zero carbon emissions by 2050, as has the EU, USA and Gambia.

       China has pledged to reach net-zero by 2060, as have Russia and India.

       UK

       Rating: Almost Sufficient

       Net Zero target: 2050

       Attending COP26: Yes

       EU

       Rating: Insufficient

       Net Zero target: 2050

       Attending COP26: Yes

       USA

       Rating: Insufficient

       Net Zero target: 2050

       Attending COP26: Yes

       China

       Rating: Highly insufficient

       Net Zero target: 2060

       Attending COP26: Via video link

       India

       Rating: Highly insufficient

       Net Zero target: 2060

       Attending COP26: YEs

       Russian Federation

       Rating: Critically insufficient

       Net Zero target: 2060

       Attending COP26: No

       The Gambia

       Rating: Sufficient

       Net Zero target: 2050

       Attending COP26: Unknown

       Nigeria

       Rating: Almost Sufficient

       Net Zero target: 2050 - 2100

       Attending COP26: Yes

       Nepal

       Rating: Almost Sufficient

       Net Zero target: 2050

       Attending COP26: Unknown

       Morocco

       Rating: Almost Sufficient

       Net Zero target: -

       Attending COP26: Unknown

       Countries were rated by Climate Action Tracker, which checks national targets against the goal to limit global warming below 1.5C.

       The danger of climate change is already apparent, with a report by the World Meteorological Organisation, showing extreme weather events - such as fierce heat waves and deadly floods - are the new normal.

       Prime Minister Boris Johnson told the BBC that climate change was "the biggest threat to humanity", saying it posed a "risk to civilisation basically going backwards".

       With COP26 events to last all week, world leaders will work on future pledges and ways to reduce global pollution.