Extract from ABC News
The last 10 years have been the hottest on record. (ABC News: Chris Lewis)
It's official — 2024 was the hottest year on record and the first calendar year in which the earth was more than 1.5 degrees Celsius warmer than pre-industrial times.
That's a significant number, because it's the target that world leaders agreed to under the landmark Paris Agreement in 2015, to try to limit global warming.
But, while the hot year certainly isn't good news, this breach of 1.5C doesn't mean we've broken the Paris Agreement.
Let's break down why that is, what it means for our climate and weather, and where 1.5C marker came from in the first place.
What is the Paris Agreement?
The Paris Agreement is a legally binding international treaty on climate change.
It was the first time that almost all countries agreed to work together to limit global warming and adapt to climate change, with 196 parties signing on.
Australian students gather to demand the government take action on climate change. (Photo by Mark Metcalfe/Getty Images)
As a part of the agreement, countries agreed to substantially reduce global greenhouse gas emissions to keep the long-term global average surface temperature to "well below 2C" above pre-industrial levels.
They also agreed to "pursue efforts" to limit warming to 1.5C above pre-industrial times, using the years between 1850-1900 as the baseline.
What does 1.5 degrees of warming mean?
An increase of 1.5C or 2C may seem small on the surface. After all, you don't really notice the difference between a 27C and 29C day.
But Professor David Karoly, a climate scientist at the University of Melbourne and the Climate Council, said an increase of 1.5C on a global scale meant many more extremely hot days on the ground.
"1.5C of global warming also means more that 2C of warming over land areas, which is where people live," he said.
Professor David Karoly from the University of Melbourne says small temperature increases matter. (Supplied: David Karoly)
The 1.5C target was chosen because the Intergovernmental Panel on Climate Change (IPCC) indicates that crossing that threshold risks unleashing far more severe climate change impacts, including more frequent and severe droughts, heatwaves, rainfall, and coastal flooding from storm surges.
Just small increases in warming are incredibly significant. (Supplied: Climate Council)
Professor Karoly said no level of global warming was absolutely safe, however.
"We've seen that with the impacts of climate change over the last 10 and 20 years already. Increases in heatwaves and health impact, increases in extreme rainfall, increases in drought, increases in bushfires have already been experienced," he said.
The number of weather-related disasters has increased five-fold since 1970, according to the World Meteorological Organization (WMO).
So, have we breached the Paris Agreement?
The good news is, we haven't got there yet.
Yes, the world was 1.5C warmer than pre-industrial times this year.
But the Paris Agreement is talking about a long-term change. This is generally looked at as an average over a period of 20 years.
In other words, one year isn't considered "long term" in the climate world.
This is because natural variability — including phases in the ocean such as El Niño and La Niña, as well as volcanic eruptions — can boost the temperature fluctuations a bit year-to-year.
Simmering oceans around Australia are fuelling a hot, wet summer ahead. (ABC: Chris Lewis)
According to the latest IPCC report, human activities are estimated to have caused approximately 1.0C of global warming above pre-industrial levels to 2020.
However, the rate of warming has been "ramping up" in recent years, according to Professor Karoly.
Has 2024 given us a taste for a 1.5C world?
2024 was a year where floods gave way to heatwaves, and devastating storms dominated the headlines.
Professor Karoly said, to some degree, this year has given a taster of the sort of extreme weather and climate events associated with a 1.5C warmer world.
For instance, The Global Water Monitor found daily rainfall records were 52 per cent more common around the world in 2024 compared to the 1995-2005 average.
The increase in daily rainfall extremes has resulted in significant flash flooding events around the globe, including the devastating flooding in Spain in October.
People work to clear a mud-covered street with piled up cars in Paiporta. (Reuters: Eva Manez)
The hurricane and typhoon season in the Northern Hemisphere was also particularly destructive, featuring several severe and record-breaking systems.
Meanwhile, at least 1,300 people died during last year's Hajj pilgrimage to Mecca amid extreme heat.
A Muslim pilgrim pours water on his head to cool down from the heat, as he takes part in the annual hajj pilgrimage in Mina in June 2024. (Reuters: Mohammed Torokman)
But Professor Karoly said impact needed to be looked at over a longer period of time to see the true trends.
"What we've got to think about and consider is that 1.5 degrees of warming maintained for 10 years or longer takes a while to then manifest, the impacts because many of the local and regional impacts vary from year to year due to the natural variability," he said.
What happens if the Earth reaches 1.5 degrees?
Unfortunately, short of some kind of large and unexpected event, Professor Karoly said the Earth was all but guaranteed to hit the 1.5C mark.
Estimates from the latest IPCC report expect global warming to reach 1.5C between 2030 and 2052, though Professor Karoly said it's likely to be earlier based on recent years of data.
This is due to the amount of greenhouse gases already in the atmosphere, which we continue to emit.
The Paris Agreement is designed to phase out fossil fuels and limit global temperature increases. (Getty Images: baranozdemir)
"[To prevent it from happening] we would need to achieve net zero emissions really, really quickly , and be able to suck out significant amounts of carbon dioxide that are already in the atmosphere," he said.
"We are nowhere near achieving net zero emissions, we haven't even achieved a peak yet, emissions are still increasing."
Scientists had hoped 2024 was the year that we would see emissions start to fall. Instead, they grew again, reaching record highs — though the rate is slowing.
But he said that did not mean we should give up on efforts to drastically reduce greenhouse gas emissions, as any "degree of warming we can prevent will be for the better".
"It's only by reducing this climate pollution in Australia and in all other countries that we can seek to limit global warming and not overshoot by too much," he said.
"There is still hope. We have already seen substantial reductions in greenhouse gas emissions in Australia."
But in Professor Karoly's view, that's not enough. He said unless Australia reduces its coal and gas exports, it won't be able to sufficiently lower its overall emissions.
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