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06/07/2022
By Brooke Coupal

Understanding how climate changed in the distant past is helping researchers forecast its future.

鈥淧eople are always asking, 鈥榃hy do you care about the climate from thousands of years ago?鈥� But really, it helps us contextualize the changes that we鈥檙e seeing with the climate right now. We can get a sense of what we can expect to see in the future,鈥� says Environmental Earth and Atmospheric Sciences Asst. Prof. Christopher Skinner. 鈥淚t鈥檚 super important to know the past to project the future.鈥�

Skinner and a team of researchers from across the country investigated how the temperature on Earth changed over the past 10,000 years and discovered that vegetation played a major role.

鈥�51视频 6,000 years ago, we had a very different distribution of plants on the Earth, and because of that, it was 1.5 degrees Fahrenheit warmer than it is today,鈥� says Skinner, who co-authored a paper published in on the team鈥檚 findings.

Earth鈥檚 orbit shifted during that time period, which increased the amount of energy the planet was getting from the sun. This led to vegetation growth in the Northern Hemisphere, including in the Sahara Desert and the edge of the Arctic.聽

鈥淚t was wildly different. We have a lot of evidence that it was a lot greener at that time,鈥� Skinner says.

Plants absorb a lot of the sun鈥檚 energy due to their dark green color, so when there was an abundance of vegetation, Earth absorbed more solar energy, and that caused the temperature to rise.

Earth鈥檚 orbit changes in three distinct ways 鈥� through eccentricity (shape of Earth鈥檚 orbit around the sun), precession (the direction that Earth鈥檚 axis points as it moves around the sun) and obliquity (angle of Earth鈥檚 tilt on its axis) 鈥� and all three changes need to align to repeat what happened 6,000 years ago. Skinner says the planet is thousands of years away from that occurring again; however, warmer temperatures are projected in the future due to our fossil fuel use, and this will impact the distribution of vegetation on Earth.

鈥淧lants can be very sensitive to the climate, and so as we change the climate with increased greenhouse gases from fossil fuel use, the distribution and characteristics of plants are going to start changing, and that change in plants is going to then have an influence on our climate,鈥� he says. 鈥淭his is a pretty big deal.鈥�

Skinner adds that it鈥檚 important for researchers to take changes in vegetation into account when making predictions about future climates.

鈥淚f we鈥檙e thinking about climate change and we鈥檙e trying to project what鈥檚 going to happen, the way we do that is through climate models, and if the models don鈥檛 include these changes in vegetation, then our projections are going to be wrong,鈥� he says.

The ENSO Impact

Another factor Skinner says is important to consider when making climate projections is the El Ni帽o-Southern Oscillation (ENSO), which is a recurring pattern of changes in water temperature in the Pacific Ocean. Skinner and a team of researchers looked at historical records and identified ENSO as the main driver of concurrent droughts.

These droughts, which impact multiple regions at the same time, can be detrimental to the Earth鈥檚 socioeconomic systems, especially the agricultural sector. The researchers鈥� findings, which were published in the journal , point to the challenges ahead, with concurrent droughts expected to increase throughout the century.

鈥淒rought in one region can be really bad for the people that live there, but hopefully, our global agricultural system is set up such that if there鈥檚 a drought in one region that impacts food production, we can make up for that by increasing exports from other regions that grow the same crops,鈥� Skinner says. 鈥淏ut that system sort of fails when multiple regions experience drought at the same time. We don鈥檛 necessarily have the support system to handle that.鈥�

Scientists can predict ENSO with some regularity, and that can allow industries to plan accordingly for impending concurrent droughts.

鈥淕enerally, several months in advance, you have an idea of whether you鈥檙e going to have a particular pattern of sea temperatures in the Pacific Ocean, so if we know that a certain phase of ENSO is coming, we have a better sense of whether or not there鈥檚 going to be a concurrent drought in the preceding months,鈥� Skinner says.

Incidents of ENSO are projected to become more likely in the future as the planet gets warmer due to increased fossil fuel use. According to , Earth鈥檚 average surface temperature has risen by about 2 degrees Fahrenheit since the late 19th century, an increase caused largely by the rise in carbon dioxide emissions and other human activities.

鈥淚f we want to stop these concurrent drought events from happening, it鈥檚 pretty clear that the best way to do that is to end our reliance on fossil fuels,鈥� says Skinner. 鈥淲e need to take action immediately.鈥�