What's the difference between 1.5°C and 2°C of global warming?

World leaders and scientists have stressed that 1.5 degrees Celsius is the magic number….when it comes to saving our planet.

The 2015 Paris Agreement commits countries to limit the global average temperature rise to below 2 degrees Celsius above pre-industrial levels…

but they’re aiming for 1.5.

So what difference does .5 of a degree actually make?

The world has already heated to around 1.1°C above pre-industrial levels….

Scientists say crossing the 1.5°C threshold risks unleashing far more severe climate change effects on people, wildlife and ecosystems.

Just this year, torrential rains flooded China and Western Europe.

The Pacific Northwest sweltered in record heat.

And Greenland saw massive melting events.

Climate scientist Daniela Jacob at the Climate Service Center Germany says - quote - "Half a degree means much more extreme weather, and it can be more often, more intense, or extended in duration."

The difference between 1.5°C and 2°C is also critical for Earth's oceans and frozen regions.

Warming of 1.5°C would destroy at least 70% of coral reefs, but at 2°C more than 99% would be lost.

Take Australia's Great Barrier Reef, for example.

A recent study has found that the corals could still have a chance to survive...if global warming is kept to 1.5 degrees.

Professor Terry Hughes of the Australian Research Council's Centre of Excellence for Coral Reef Studies is the study's lead author.

"The trajectory of the Great Barrier Reef will depend critically on how much hotter the planet gets. If we can hold global warming to 1.5 degrees global average warming then I think we'll still have a vibrant Great Barrier Reef.// But if we go to 3, 4 degrees of global average warming which is tragically the trajectory we are currently on then there won't be much left of the Great Barrier Reef or any other coral reefs throughout the tropics." (https://www.reutersconnect.com/all?id=tag%3Areuters.com%2C2021%3Anewsml_WDF26L5C7&share=true)

To avoid crossing the 1.5 degree threshold requires almost halving global CO2 emissions by 2030 from 2010 levels…

and cutting them to net-zero by 2050 –

It's an ambitious task that scientists, financiers, negotiators and activists who continue to debate how to achieve and pay for.

(SOUNDBITE) (English) COP26 PRESIDENT, ALOK SHARMA, SAYING:

"….we should try and keep 1.5 (degrees Celsius) within reach. And I hope that is the spirit with which negotiators will continue to approach these discussions."