Future Temperatures: How hot will Earth be due to climate change?

5 minute read

Updated on: 25 Jun 2020

How will temperatures change in the future?

Climate models use several different scenarios of human behaviour to predict different possible future changes in temperature [ref1,ref2]. These predictions, along with a range of possible results, are shown in the graph below [ref].

Image of Future Temperature Predictions

Future Temperature Predictions [ref]

The green line in this graph represents a future where there is no change or addition to current climate policies [ref1,ref2,ref3]. It’s estimated that this would cause 4.5°C of global warming by 2100 [ref1,ref2].

If we implement climate policies such that CO₂ emissions peak at roughly 40Gt per year around 2040 [ref1,ref2] and become roughly constant at 15Gt per year after 2080 [ref], the light blue line is more likely. This corresponds with 2.5°C of warming by 2100 [ref1,ref2].

The dark blue line represents a future where extremely rigorous and strict climate policies [ref] are put into place during 2020 [ref]. This would still cause 1.6°C of global warming by 2100 [ref1,ref2].

For the past 250 years, humans have been releasing greenhouse gases into the atmosphere [ref], which has caused the Earth to warm by roughly 1.1°C [ref]!

Image of Abnormal Warming

Abnormal Warming [ref]

As the planet warms, melting ice, thawing permafrost, and other responses from the Earth itself will make temperatures rise even more (take a look at the chapter on feedbacks for more on this) [ref1,ref2].

Image of Positive Feedback

Positive Feedback

Why are we worrying about climate change today?

Greenhouse gases and positive feedbacks are causing the Earth to warm unusually quickly [ref]. Over the past century it has warmed about 10 times faster than the average increase in temperature after every ice age [ref].

Despite there also being rapid and large changes in temperature in the distant past [ref1,ref2], current global warming is dangerous because humans have not experienced changes of this scale and speed before [ref], so it will be challenging for us to adapt [ref1,ref2].

Image of Difficulty in adapting

Difficulty in adapting

For example, the last time Earth’s average temperature reached 4.5°C above the pre-industrial levels was 5 million years ago [ref]. Back then, humans [ref] and even mammoths [ref] had not evolved yet!

Image of Same Temperatures in History

Same Temperatures in History [ref1,ref2]

Realistically, how are temperatures going to change under current policy?

How much greenhouse gas we release depends mainly on how much energy we use and on how it is produced [ref1,ref2].

These factors are dictated by politics, economics [ref1,ref2], population size and energy use per person.

As part of the Paris Agreement, every country pledged to limit global temperature rise to well below 2°C above pre-industrial levels, and preferably below 1.5°C [ref1,ref2].

However, if we look at the promises made by countries to reduce greenhouse gas emissions, currently over 7 out of 10 countries won’t succeed in achieving their Paris Agreement pledges [ref]! On average, emission reduction promises must become 5 times more effective within the next decade to keep temperatures below 1.5°C [ref1,ref2,ref3].

Many scientists believe we have little hope of restricting global warming to 1.5°C or even 2°C [ref1,ref2,ref3,ref4,ref5,ref6].

In fact, if global warming continues at its current rate, there is a 66% chance that we will reach 1.5°C of warming between 2030 and 2052 [ref1,ref2].

But global warming is actually getting faster and faster [ref], so drastic action must be taken now to reduce emissions to limit these rising temperatures [ref1,ref2].

You’ll learn more about the solutions to this problem in later courses!

Next chapter!