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How do we measure climate change?
Degrees of warming tell us how much the earth has warmed since pre-industrial times
April 29, 2024

One of the most useful tools for measuring climate change is degrees of warming, which tell us how much the global average temperature has increased since pre-industrial times. In 2024, we’re moving past 1°C of warming and toward 1.5°C—a seemingly small increase of 0.5 degrees with big impacts. Degrees of warming can help you understand the changes that have already occurred, the significance of 1.5°C, and where we are headed.

What are degrees of warming?

Degrees of warming use degrees celsius to measure Earth’s average temperature compared to the era before industrialization and the widespread use of fossil fuels that came with it. They tell us how much the earth has warmed since that era and allow us to track the pace and scale of global climate change.

To determine degrees of warming, scientists calculate the global average temperature from locations across the globe and compare that average to the relatively stable average that existed before industrialization. The difference between the current average temperature and the relatively stable average that existed before industrialization is the degree of warming the planet has reached, or the warming scenario we are living in.

Degrees of warming are used by the scientific community and are useful to everyone. Measuring and understanding them helps in keeping up with climate change. You’ll see them wherever you’re learning about climate, including on our maps:

Probable Futures maps use degrees of warming, or warming scenarios, in 0.5°C increments to model past and future climate conditions. To explore what conditions were like in the recent past, or might resemble in the future, select a warming scenario in any given map.

The 1.5°C threshold

When the Paris Agreement of 2015 established 1.5°C as the temperature increase to avoid, this specific degree of warming became well-known in the context of climate action. In 2015, 1.5°C of warming was an outcome we could avoid if nations mobilized quickly and dramatically to reduce their greenhouse gas emissions. As of 2024, many scientists have concluded, based on our current degree of warming, that avoiding 1.5°C is no longer possible.

When reading headlines about whether or not we have passed 1.5°C, or whether passing 1.5°C is an inevitability, consider how degrees of warming are calculated. Because degrees of warming are average measures of Earth’s complex, dynamic systems, using data from the recent past, it’s impossible to pinpoint a precise moment when 1.5°C becomes our reality. Instead, we are trying to capture a moving target, looking at data from year to year, over several years, and across decades to assess the moment when Earth’s average temperature has breached a certain threshold.

For example, in January 2024, the non-profit research organization Berkeley Earth released their Global Temperature Report for 2023. The report led with an important conclusion: Temperatures recorded over the 12 months of 2023 indicated warming of 1.54°C above the pre-industrial average. This marked the first time that a single year had been more than 1.5°C above that historic average. However, Berkeley Earth clarified that this finding only reflected data from the year 2023, in which an emerging El Niño, along with other natural factors in the climate, contributed to record-breaking heat. Looking at long term trends over the past 20-30 years, Berkeley Earth puts the planet at an average of 1.3°C of warming in 2024. 

The difference in these numbers reflects the difference in how they are calculated: The average degree of warming the planet has reached has to be deduced from a representative sample of annual average temperatures in the recent past. What most scientists agree on is that we are close enough to 1.5°C that this degree of warming is inevitable: Our current rate of greenhouse gas emissions, combined with the warming effect of our past emissions, means we are “locked in” to passing 1.5°C at some point in the near future.

What can degrees of warming tell us about a changing climate?

We can apply degrees of warming to give insight into climate change in the form of benchmarks, timelines, and projections. Benchmarks can tell us what targets we want to, or need to, aim for, timelines can tell us how far in the future changes may occur, and projections can tell us what those changes might mean for human and natural systems. 


An example of a benchmark for a degree of warming would be the Paris Agreement, which identified 1.5°C of warming above pre-industrial levels as a warming scenario to avoid, partly due to the climate impacts associated with that warming scenario (increased risks of drought, wildfire, floods, and dangerous heat). Entities from governments to companies use degrees of warming in this way to motivate behavior change based on what is important for their community, goals, or scope of influence.


It’s inaccurate to tie a degree of warming to a specific year in the future. The timeline of hitting different degrees of warming depends on our greenhouse emissions, which are subject to changing trends in human behavior, policy, economics, and more. If we generate more, or less, greenhouse gas emissions than anticipated, we might reach a degree of warming earlier or later. It’s more helpful to think of degrees of warming in terms of past, recent past, impending, and potential warming scenarios. Using degrees of warming instead of time allows us to portray scenarios that we can avoid, better understanding the consequences of further warming, and hopefully motivate action to reduce and eliminate greenhouse gas emissions.


Climate science has given us a tremendous gift—reliable projections of climate conditions tied to specific degrees of warming. Using tools like the Probable Futures maps to explore these projections, anyone can anticipate potential changes to conditions like precipitation, drought, heat, and wildfire. 

Even slight changes in degrees of warming have major implications for these climate impacts: Probable Futures maps show that going from 1°C to 1.5°C, causes freezing days in Denver, Colorado to drop by 15%, New York City’s 1-in-100 year storm to become twice as likely, the probability of extreme drought in the Amazon to increase by 10%, and, for the first time in its modern history, Sicily to experience temperatures above 45°C (114°F). 

These projections are a valuable tool, allowing us to anticipate and prepare for changes. The more we understand about our current degree of warming and what is impending, the better we can use these tools to anticipate and prevent bad outcomes.

The changes described above all come from data in Probable Futures maps, freely available on our platform. Want to learn more about our changing climate? Read Heat to get started.