When modeling the climate, it pays to look long term. Most climate change models illustrate what the Earth will look like by the year 2100. A mere 70 years away, we see that the Earth will undergo significant changes depending on continued CO2 emission. However, to truly understand the full impact of a warming climate, it is important to extend these models further into the future. In a recent piece in Global Change Biology, a team of researchers from Montreal and the United Kingdom extended modeling to 2500, and show that within the next 500 years, climate change could make the Earth unrecognizable.

The world would look very different depending on how much we mitigate carbon emissions. These pathways were developed by the Intergovernmental Panel on Climate Change and range from a high mitigation, low emission scenario (RCP 2.6) to a low mitigation, high emission scenario (RCP 6.0). In the high mitigation scenario, the reliance on fossil fuels on a global scale is decreased and we reach negative CO2 emissions by late century. Lower mitigation scenarios show a lack of governance and increased reliance on fossil fuels. All but the highest mitigation scenario do not meet the limit of warming of 2 degrees C set by the Paris Agreement.

One Best Case Scenario – A World With Limited Carbon Emissions

In their “best-case scenario” (RCP 2.6), the world drastically cuts back on carbon emissions. In this model, the researchers show that global temperature increases to a mean value of about 0.5 C mid-century, and then decreases. Most of the average temperature increase occurs over the poles and middle latitudes. But even in this model sea levels continue to rise even beyond mid-century, since it takes a significant amount of time for warmer water to mix deep within the ocean. Overall, the researchers show that the sea level may rise nearly a quarter of a meter.

A Sadly Realistic Scenario – A World With Little Mitigation

When things get worse, they get a lot worse. In a future with “moderate-high” greenhouse emissions and few efforts to mitigate these gasses, our world is truly transformed.

First, there is an increase in heat. In this model (RCP 6.0), the world will be 2.2 degrees C higher in 2100 than today. And by 2500, the world will be a full 4.6 degrees C higher.

It is difficult to fully appreciate what these numbers mean. After all, a few degrees C doesn’t sound like much. But the authors point out that these numbers would fully restructure the world’s biomes. To show how, the authors paint a picture of three different regions of the world – the American Mid-west, India, and the Amazon.

The American Mid-west today is a main production hub of crops such as wheat and corn. It has cold winters and hot summers. Under the RCP 6.0 model, the summer temperature would increase from a mean of 28 degrees C to 36 degrees C (which is more in line with summertime temperatures seen in India today). This would cause significant “heat stress” for a good portion of the year, at levels that can be fatal to humans. Perhaps most markedly, it would no longer serve as the breadbasket of the region. Agriculture would be increasingly challenging, and crops that the region is known for would be replaced by subtropical forests.

India does not fare much better. In the RCP 6.0 scenario, this place that is already hot may become completely uninhabitable. Heat would be so intense that most people would need personal protective equipment. Monsoons would increase as tropical rainforests extend across the country. These factors would lead to a population shift across the globe.

Finally, the authors look at the Amazon. This biome, so important for the globe today, would be completely transformed. Today, three million different species, 1/3 of the biodiversity of the planet, call the Amazon home. In the RCP 6.0 scenario, the jungle would die back and be replaced by bare soil. Precipitation would be disrupted. This, along with high temperatures, would displace human populations within the area.

Global Effects on Agriculture

Under the RCP 6.0 scenario, large parts of Africa, South America, the Middle East, and Australia would suffer severe heat stress for nearly half the year.

The authors looked at 10 different crops – cassava, maize, potato, rice, sorghum, soybean, sweet potato, taro, wheat, and yam. In the RCP 6.0 model, wheat would no longer be able to grow in the middle of North America and Asia. Most crops, especially wheat, potato, and cassava, will lose land fit for growth. Soybean and maize are the only two crops that will gain suitable land for cultivation. Most crops will have to move a full 10 degrees towards the poles, transforming northern latitudes into the new breadbasket, while places like the once rich Amazon become barren.

Why Look Long Term?

The year 2100 is only 79 years away. To fully understand the effects of climate change, we must look at how the Earth will be affected in the longer term.

The global temperature has already increased 1 degree C from pre-industrial levels. With increasing temperatures, we not only will see biomes be restructured but a massive redistribution of human population. Food production will change, and infrastructure will need to be adapted. Governments have to be ready.

Or conversely, we need to act now to mitigate carbon emissions.

“It is now clear that without deep and rapid reductions in greenhouse gas emissions, climate change will continue for centuries into the future,” the authors say.