How does a 0.5 degree Celsius difference affect the global future?

If the Earth warms by 2 degrees Celsius instead of 1.5 degrees Celsius, people, wildlife and ecosystems will all suffer severe consequences.

At COP26 - the United Nations climate change summit taking place in Glasgow, Scotland, from October 31 to November 12, world leaders repeatedly emphasized the need to limit levels global warming at 1.5 degrees Celsius. With the 2015 Paris Agreement, countries committed to keeping the increase in average global temperature below 2 degrees Celsius above pre-industrial average temperatures, and also aim for 1.5 degrees Celsius.

The parched ground of the Jaguari Dam, part of the Cantareira reservoir system, during drought in Joanopolis, Brazil, October 8, 2021. (Photo: Reuters/Amanda Perobelli)

Exceeding the 1.5 degrees Celsius threshold risks much more severe climate change impacts on people, wildlife and ecosystems. To prevent this from happening, global CO2 emissions must fall by almost half from 2010 levels by 2030 and reach net zero by 2050. Scientists, financiers, negotiators and activists activists at COP26 are discussing how to achieve and pay for this ambitious goal.

The world has already warmed about 1.1 degrees Celsius above pre-industrial times. Each of the past four decades has been hotter than any decade since 1850. "We haven't experienced such global warming in just a few decades. 0.5 degrees is synonymous with extremes. more severe weather events, which can be more frequent, more intense or longer lasting," said climate scientist Daniela Jacob at the German Center for Climate Services.

This year, torrential rains hit China and Western Europe, killing hundreds of people. Hundreds more died as temperatures in the Pacific Northwest hit record highs. Greenland experienced major ice melt events, the Mediterranean and Siberia were ravaged by wildfires, while parts of Brazil suffered record-breaking droughts.

Houses destroyed by floods in Mayschoss, Germany, on July 29, 2021. (Photo: Reuters/Andreas Kranz)

Such effects will be exacerbated if the temperature rises to 1.5 degrees Celsius or more. "Climate change is already affecting every inhabited region of the world," says climate scientist Rachel Warren at the University of East Anglia.

"With each increase in global warming, the changes in extreme weather events also become larger," said climate scientist Sonia Seneviratne at the Swiss Federal Institute of Technology (ETH Zurich) ) said.

For example, heat waves will be more frequent and severe. An extreme heatwave occurs every 10 years when the climate is not affected by humans, 4.1 times a decade when temperatures increase by 1.5 degrees Celsius and 5.6 times when the temperature increases. is 2 degrees Celsius, according to the Intergovernmental Panel on Climate Change (IPCC). If the temperature increases by 4 degrees Celsius, this phenomenon could happen 9.4 times per decade.

Warmer atmospheres can also trap more moisture and make torrential rains more frequent, increasing the risk of flooding. Warm atmospheres also increase water evaporation, leading to more severe droughts.

The difference between 2 degrees Celsius and 1.5 degrees Celsius is crucial for the oceans and frozen regions on Earth.

"At 1.5 degrees Celsius, there's a good chance we'd prevent most of the ice sheet in Greenland and west Antarctica from collapsing , " explains climate scientist Michael Mann at Pennsylvania State University. That should help limit sea level rise later in the century, although the change could still be large enough to cause coastal erosion and inundate some small island nations and coastal cities.

However, the ice sheets could collapse if the rise exceeds 2 degrees Celsius, Mann said. By that time, sea levels could rise by up to 10 meters - although experts are not sure how quickly that will happen.

Global warming of 1.5 degrees Celsius will destroy at least 70% of coral reefs, but with a 2 degrees Celsius increase, more than 99% will die. This will destroy fish habitat and severely affect reef-based communities.

The difference between 2 degrees Celsius and 1.5 degrees Celsius will also affect food production. "If several important grain-growing regions lose their crops at the same time, food prices could spike and famine would occur in large areas around the world," said climate scientist Simon Lewis at the University of College London commented.

A warmer Earth could allow mosquitoes that carry diseases like malaria and dengue fever to live and operate on a broader scale. However, a 2°C increase would also result in more habitat loss for insects and animals than a 1.5°C increase. The risk of wildfires, a threat to wildlife, also increases.

Flames rise during a forest fire in the village of Galatsona, island of Evia, Greece, August 9, 2021. (Photo: Reuters/Nicolas Economou)

Global warming increases the risk of reaching "tipping points" . At that time, Earth's systems exceed the allowable threshold and cause irreversible effects. Scientists have not been able to determine exactly when the blue planet will reach the tipping point.

For example, drought, reduced rainfall, and continued destruction of the Amazon forest could cause the rainforest system to collapse and release CO2 into the atmosphere instead of storing it. Warming Arctic permafrost can cause perennial frozen biomass to decompose, releasing large amounts of carbon.

"That's why continuing to use fossil fuels and emissions is so risky. We're increasing the likelihood of exceeding one of the tipping points , " Lewis said.

To date, the climate commitments that countries have submitted to the United Nations agency are bringing the world closer to the threshold of warming of 2.7 degrees Celsius. The International Energy Agency (IEA) on November 5. The new commitments announced at the COP26 summit - if implemented - could keep the rise below 1.8 degrees Celsius, although some experts are skeptical of this estimate.

A global warming of 2.7 degrees Celsius will lead to " unlivable " heat in the tropics and subtropics at certain times of the year. Biodiversity will be severely reduced, food security will be reduced, and extreme weather events will be so intense that it is beyond the capacity of most urban infrastructure.