Why it matters that Earth is on the brink of 1.5 degrees Celsius in warming

(NEW YORK) — Earth is already on the brink of surpassing an internationally agreed-upon threshold for climate warming, relative to pre-industrial levels, which could bring disastrous consequences to regions around the world, according to researchers.

A study published Monday in Nature Climate Change, which assessed the size and uncertainty of the remaining global carbon budget, found that by early 2029, if greenhouse gases continue to be emitted at the current rate, the planet may be unable to remain below the threshold of 1.5 degrees Celsius of global warming.

This time frame projects that the carbon budget — that is, the net amount of carbon dioxide that humans can still emit without exceeding 1.5 degrees — will run out three years earlier than the previously expected expiration year of 2032.

Why keeping the planet below 1.5 degrees Celsius of warming is critical

The exact figure of 1.5 degrees Celsius of warming is less important than keeping global warming as far below that figure as possible. But researchers say the likelihood of doing so is waning.

Limiting global warming to less than 1.5 degrees Celsius since pre-industrial levels was outlined when the United Nations Framework Convention on Climate Change created the Paris Agreement, an international treaty signed by the majority of the world’s countries in 2015 in a global effort to mitigate climate change.

The Nature Climate Change study researchers state that if carbon dioxide emissions remain at current levels, the remaining carbon budget will be exhausted by early 2029. In 2021, the U.N. Intergovernmental Panel on Climate Change (IPCC) determined a carbon budget of 500 billion metric tons would keep global warming below 1.5 degrees Celsius until mid-2032. The newest assessment brings the threshold three years closer.

While climate models can’t predict exactly when irreversible impacts of climate change may be triggered, going beyond the 1.5 degree benchmark heightens the risk of warming-related catastrophes, according to researchers.

A 2018 report by the IPCC predicts that amount of warming will threaten coral reefs; melt Antarctic ice sheets, contributing to sea level rise; cause the ocean to become more acidic; and negatively impact crops in some parts of the world.

The 1.5-degree change alone is predicted to wipe out coral reefs; melt Antarctic ice sheets, which in turn could contribute to rising sea levels; cause the ocean to become more acidic; and negatively impact crops in some parts of the world, all according to a 2018 report by the IPCC.

Despite the new assessment of exhausting the carbon budget by 2029, the planet is now so close to exceeding the 1.5-degree warming threshold that the exact timing isn’t significant, says Rob Jackson, a professor of Earth System Science at Stanford University.

“The world will blow past 1.5 [degrees] C well before today’s kindergarteners finish high school,” Jackson, who was not involved in the Nature Climate Change study, told ABC News.

Every tenth of a degree makes the impacts of climate change worse, Zeke Hausfather, a climate scientist at Berkeley Earth, a California-based nonprofit focused on land temperature data analysis for climate science, told ABC News.

“So even if we’re going to miss our most ambitious target, which seems increasingly likely, that just ups the pressure to keep it from rising even further,” he said.

Once 1.5 degrees of warming is reached, the next countdown will be to 2 degrees Celsius of warming, which will likely occur in the 2040s, according to the study.

Just half a degree more of warming will lead to even more disastrous climate-related disruptions, scientists say. Should global temperatures further warm up to 3 degrees, research shows the result would be unlivable conditions in much of the world.

What will happen when these warming thresholds are surpassed?

Just how disastrous would be the consequences the planet and its inhabitants will experience as temperatures climb? Climate researchers say the most drastic result will take the form of extreme weather events.

Droughts are expected to become worse and last longer. Warmer ocean waters mean the number of strong hurricanes is expected to increase, as will the likelihood that they will quickly gain strength as they approach coastlines. Wildfires will become more intense due to hotter climates and drying landscapes. Melting ice sheets will leave some populated coastal regions underwater.

Some consequences of climate change caused by warming global temperatures have already begun to emerge, evident in extreme weather events that have occurred in recent years. Global water cycles have already become ”increasingly erratic” as a result of warming temperatures, according to a report by the World Meteorological Organization, published earlier this month. In addition, sea levels are rising and will continue to do so, especially as rapid ice melting at the poles persists.

It’s not too late to curb climate change

While both time and the carbon budget may be running low, it’s not too late to drastically curb greenhouse gas emissions to slow global warming, according to climate scientists.

The situation could “dramatically change” with a severe cut in greenhouse gas emissions, as well as widespread adoption of clean energy, Jackson said.

To keep global warming to no more than 1.5 degrees Celsius, current emissions need to be reduced by 45% by 2030 and reach net zero by 2050, according to the U.N.

While many countries, including the U.S., U.K. and European Union, have made pledges to reduce emissions to net-zero by 2050, the world’s largest emitters have the further responsibility to increase and encourage efforts to cut the use of fossil fuels around the world, according to experts.

Increasingly ambitious climate policies being adopted by countries across the globe are now beginning to have a positive impact on warming mitigation. However, efforts are not moving fast enough to keep up with the current rate of global warming.

“The fact that we have made some progress should encourage us that progress it possible,” Hausfather said. “…We’re just not doing things fast enough to avoid potentially dangerous levels of warming.”