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Would the climate be warming without humans?

Image: Joseph Chan

Would the climate be warming without humans?

 Summary

 

In the 4.54 billion years since Earth formed, natural climate factors or forcings have changed Earth’s climate, making it warmer or cooler many times, for different reasons outlined in the menu on this page.

The nice weather we’ve had for the last 4,500 years allowed us to build a global civilization. Ironically, burning fossil fuels and eradicating natural ecosystems that helped keep the carbon cycle in balance, has dangerously destabilised the climate. Today, when all of the natural forcings are added together, Earth should be cooling. Instead, we’re warming rapidly (Figs. 1 & 2).

We know from fundamental laws of physics that greenhouse gases trap heat in the atmosphere, and why that changes the chemistry of the atmosphere, making it warmer. We also know we humans are emitting lots of these greenhouse gases (Video 2). No matter how much we might wish otherwise, there is no negotiating with the laws of physics and chemistry: we humans are entirely responsible for turning the heat nob on Earth’s thermostat to ‘high’.

Any opinion to the contrary would need to explain why global temperatures are rising instead of falling, and explain why fundamental laws of physics and chemistry have stopped working.

The good news is that we can use nature to capture and store excess greenhouse gases back in the ground, so we can limit the impacts.

 Summary

 

In the 4.54 billion years since Earth formed, natural climate factors or forcings have changed Earth’s climate, making it warmer or cooler many times, for different reasons outlined in the menu on this page.

The nice weather we’ve had for the last 4,500 years allowed us to build a global civilization. Ironically, burning fossil fuels and eradicating natural ecosystems that helped keep the carbon cycle in balance, has dangerously destabilised the climate. Today, when all of the natural forcings are added together, Earth should be cooling. Instead, we’re warming rapidly (Figs. 1 & 2).

We know from fundamental laws of physics that greenhouse gases trap heat in the atmosphere, and why that changes the chemistry of the atmosphere, making it warmer. We also know we humans are emitting lots of these greenhouse gases (Video 2). No matter how much we might wish otherwise, there is no negotiating with the laws of physics and chemistry: we humans are entirely responsible for turning the heat nob on Earth’s thermostat to ‘high’.

Any opinion to the contrary would need to explain why global temperatures are rising instead of falling, and explain why fundamental laws of physics and chemistry have stopped working.

The good news is that we can use nature to capture and store excess greenhouse gases back in the ground, so we can limit the impacts.

Fig. 1: This composite graph from Carbon Brief shows that an increase in temperature from greenhouses gases (red line) matches the warming we’ve observed (light grey line). Each of the natural and anthropogenic cooling and warming ‘forcings’ are explained in WHAT CAUSES CLIMATE CHANGE (menu at the top left).
Fig. 2: The blue line shows that with all the natural climate forcings combined, the planet should be slightly cooling. The red line shows that human factors far outweigh this cooling, even when volcanic eruptions lead to short drops in temperature. NOTE: not all areas of the planet are warming equally. The Arctic and Antarctic are warming much faster that the tropics. On average, the land surface of the Earth is about 5C warmer, and the ocean (which covers 70% of the surface of Earth) are about 0.5C warmer (IPCC, 2021). (Image: Carbon Brief)

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