Before the world (the US being the only exception) signed up to the Paris Agreement and committed to limiting climate change to 2°C (3.6°F), the World Bank released a report exposing the dangers of a 4°C (7°F) warming by the end of the century "if the global community fails to act on climate change, triggering a cascade of cataclysmic changes that include extreme heat waves, declining global food stocks, and a sea-level rise affecting hundreds of millions of people.”
That was in 2012. Now, it’s 2018 and the world is still on track for 4°C of warming. What’s more, we could see that rise as early as 2064 – though the authors of a new paper published in the journal Advances in Atmospheric Sciences say 2084 is a more realistic estimate.
This assumes greenhouse gas emissions continue at current rates and nothing is done to curb our fossil fuel use. Other studies have shown that sticking to the Paris rates are unlikely but possible and renewable energy use is on the rise, which is clearly a step in the right direction. However, carbon dioxide emissions are still rising and the report makes for grim reading.
The researchers came to this conclusion after running 39 climate models from the Coupled Model Intercomparison Project. Based on those models, there is a 74 percent chance of exceeding a rise of 4°C by the turn of the century. The researchers give 2084 as the median onset year for that warming.
Of course, warming would not affect all areas of the planet equally. The most significant change will be felt in the Arctic, which can expect a rise of 8 to 12°C (17 to 21.5°F), and land areas will experience more warming than the oceans. Elsewhere, the variability of temperature will be higher in the polar regions and lower in the tropics.
It's worth saying, the models try to be as conservative and cautious as possible, but there are certain variables that are hard to predict, which is why so much time and money is spent perfecting them. As the researchers point out, scientists at the Coupled Model Intercomparison Project database work to make the most accurate climate simulations possible.
So, what else can we expect from this warming?
"A great many record-breaking heat events, heavy floods, and extreme droughts would occur if global warming crosses the 4°C level, with respect to the preindustrial period," Dabang Jiang, a senior researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, said in a statement. "The temperature increase would cause severe threats to ecosystems, human systems, and associated societies and economies."
For more information on what would happen if temperatures were to rise by 4°C, check out this interactive map from the Met Office.
And if the dire environmental consequences of 4°C warming aren’t enough to convince you, consider this: sticking to the Paris Agreement could save the world a staggering $20 trillion dollars by 2100.