Earth's climate has been through a lot over the past few billion years and at this point, climate scientists have a pretty good handle on how our planet has changed over time. We talked about the future of the climate on how it's changing more quickly than the past and about the dangers of rising temperatures and more severe droughts and storms. Our methods for predicting the future of climate are a little different than those for reconstructing the past. The past leaves physical records we can study like tree rings and ice cores, the future requires us to be a little more abstract. We mostly predict the future of Earth's climate using computer models and mathematical reconstructions of our atmosphere that account for as much detail as possible to produce and accurate simulation
It has taken decades to get to the point where we can be confident that what it predicts is accurate. What the models say is that our climate is changing, and humans are making it happen. Global climate models, or GCMs, grew out of early computerized attempts to model the planet's atmosphere in the 40s and 50s. Scientists weren't even trying to predict the future, they just wanted to create a representation of the Earth's atmospheric system as it was at the time.
Example: Climate Model. Source: Phys.org
Climate models, then and now divide the earth's surface into squares of few hundred kilometres on the side. Each with different properties like air movement and surface temperature. Then, the computer calculates how all those squares interact with each other to see how things change over time. Those early models were super simple. They did things like combine land and sea into a single damp surface with no geography, it also represents the Earth as a cylinder instead of a sphere because the poles confused the computer. Thankfully, This didn't lead to a whole movement to cylinder-earthers. All this simplifying was necessary because early supercomputers were kind of limited. They used 5 kilobytes of ram, our smartphones has 500,000 times that much.
Still, it was enough to come up with a crude picture of Earth's atmospheric currents and its wet and dry regions. Eventually, climate scientists wanted more than just a model of the atmosphere, they wanted something that looked like an actual planet instead of a cylinder. They could make the model more accurate by making the chunks small, but that would take more computing power. By the late 1970s however, climate models started to be able to process more data and work more efficiently.
Source: Columbia University
in 1979, a report pulling from two climate model suggested that the Earth's temperature would increase as atmospheric carbon dioxide increased. Specifically, assuming twice as much CO2 in the atmosphere, they predicted an increase between 1.5 and 4.5 degree Celcius. These days, climate models are better. We now have the resources to ask and answer more detailed questions. Government want to know what will happen, in detail, of their country and scientists want to know what will happen if we take measures to stop global climate change, as oppose to letting emissions run rampant. With models we have now, we can produce more customized predictions based on different scenarios. For example, how much carbon dioxide will be emitted over a given amount of time & how much land will be used for agriculture. You can also use these models to run the predictions backwards.
With these constant improvements, every new prediction can be more detailed. In the last couple of decades, we've started to be able to predict for specific regions. It has been helpful for the people and governments in different parts of the world as they want to know different things.
One of the easiest thing to predict, is the globe is getting warmer. If we pump more heat-trapping greenhouse gas lie carbon dioxide into the atmosphere, the numbers come out warmer. There are factors other than greenhouse gases that the models take into account too, like particulate matter from volcanoes and coal burning power plants, which cna have a cooling effect. We know oceans will slow warming for a while by absorbing CO2, until they run out of capacity. All predictions say the warming caused by greenhouse gases will have a stronger effect.
Source : SERC-Carleton
Using models, with other tools, researched predict all kinds of effects, A comprehensive report by the US global change research program, published in 2014, lists some of the consequences and it emphasizes effects on North America but similar things happen around the world. With more and more time passing between periods of freezing temperatures, plants could experience a longer growing season. That could actually have a net positive effect of causing plants to take up more CO2, therefore less stay in the atmosphere. The good news pretty much ends there
In general, around the world and in North America, there would be changes in the distribution of precipitation including rain and snow. The changes tend toward increasing extremes. A warmer atmosphere holds more moisture, so wet regions will get wetter but models show shifts in large scale movements of air that would exacerbate dryness too.
Nasa has made an interactive climate time machine on their website which shows some of the key indicators of climate change such as temperature, sea ice extent and carbon dioxide concentrations have changed in Earth's recent history. I will take you through the interactive in the video below.
By Safwan Kasim
References
1) https://nca2014.globalchange.gov/
2) http://www.realclimate.org/index.php/archives/2008/11/faq-on-climate-models/
3) https://iopscience.iop.org/article/10.1088/1748-9326/7/4/044035/pdf
4) https://www.bbc.com/future/article/20150616-what-happens-when-the-sea-swallows-a-country?referer=https%3A%2F%2Fwww.youtube.com%2F
5) https://www.bbc.com/future/article/20150616-what-happens-when-the-sea-swallows-a-country?referer=https%3A%2F%2Fwww.youtube.com%2F
6) https://www.skepticalscience.com/climate-models.htm
7) https://earthobservatory.nasa.gov/features/GlobalWarming/page2.php
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