What is the Carbon Budget & Why 1.5 Celsius?

Photo by Markus Spiske on Unsplash

When talking about climate change it is often common to hear the term “carbon budget,” but what exactly is a carbon budget? In order to confront the mounting climate crisis, it is critical to understand what the carbon budget is. Unlike the name implies, a carbon budget is not as simple or straightforward as planning out a financial budget.

Carbon Spirals by Open Climate Data

The global carbon budget was established by the 2016 Paris Climate Agreement, referring to the maximum amount of carbon that can be emitted into the atmosphere before the planet warms to 1.5 degrees Celsius, above pre-industrial levels.

Source WRI

Why is 1.5 degrees Important?

To put it simply, once we go beyond 1.5 degrees Celsius, millions of lives will be threatened by devastating heat waves, lack of water, and sea-level rise, thus plunging entire regions into extreme poverty — and that’s just the beginning.

Carbon Spirals by Open Climate Data @ed_hawkins

The Intergovernmental Panel on Climate Change (IPCC) latest report concluded that if humans emit 580 gigatonnes of carbon dioxide (GtCO2) into the atmosphere, globally we have a 50% chance of staying below 1.5 degrees Celsius. Better yet, if we reduce our emissions to 420 GtCO2 the likelihood of staying below 1.5 degrees Celsius increases to 67%. This is what is known as the carbon budget.

Source: Climate Watch, based on raw data from IEA (2018), CO2 Emissions from Fuel Combustion, www.iea.org/statistics; modified by WRI.

Interactive Data Displaying World Greenhouse Gas Emissions in 2016 (Sector | End-Use | Gas)

At current rates of emissions, we are on track to exceed the global carbon budget by 2030. In 2018 alone 40.8 GtCO2 were emitted, making it that much more critical that we reach peak emissions within the next few years. However, staying within the carbon budget will take an unprecedented global effort.

For example, once exposed to COVID-19 it may take up to 14 days to show signs of infection. Similarly, carbon can linger in the atmosphere for decades, so carbon emitted today will have negative effects years down the road.

Several climate models depict that global carbon emissions will need to reach net-zero by 2050 in order to limit warming to 1.5 degrees Celsius. To limit warming to 2 degrees Celsius global carbon emissions will have to reach net-zero by 2070.

World Resources Institute (WRI)

The COVID-19 global pandemic can help us understand how big of a challenge the reduction in carbon emissions is. With the global economy shuttered, and the vast majority of airplanes grounded, daily carbon emissions fell global by 17% (11 to 25% for ±1σ) during the first part of 2020 (as of April) compared to that of 2019. However, with communities beginning to reopen, International Energy Agency’s (IEA) current estimates suggest that the reduction in carbon emissions could drop by 8% by the end of 2020, the single largest drop in carbon emissions since the end of World War II.

Global energy-related emissions (top) and annual change (bottom) in GtCO2, with projected 2020 levels highlighted in red. Other major events are indicated to give a sense of scale. Source: IEA Global Energy Review.

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Geoffrey von Zastrow

Geoffrey von Zastrow

Focused on climate change & sustainable international development. Twitter @von_Zastrow, IG @von_zastrow. Alumni @Columbia & the @earthinstitute