Ice- albedo and water-vapour feedbacks are much faster than the carbon-silicate weathering process removing CO2 from the atmosphere. Not just the feedbacks themselves, but the rates at which each component respond are very important. You may realise that this negative feedback tightly regulates or stabilises itself. This, in turn decreases temperature and will lead to the silicate weathering process becoming slower and subsequently less CO2 being removed from the atmosphere. As silicate weathering itself leads to the removal of atmospheric CO2 from the atmosphere this results in a decreased greenhouse effect. The higher the temperature, the faster this process happens (for a quick overview of what happens during the silicate weathering process, have a look at fig. But I mentioned that this was an example of a negative feedback and in order to understand this you must know that the process, silicate weathering (fig. This can be similarly applied to the ice-albedo feedback. The removal of CO2 then, as another greenhouse gas, helps to maintain a lower temperature, preventing increased water vapour evaporation. This is important, for example, if we think back to the positive water vapour feedback, remembering that water vapour acts as a greenhouse gas. It achieves this by sequestering atmospheric carbon dioxide. There are many of them but a major negative feedback keeping things in check is the so called silicate-weathering feedback. So, how does the planet regulate itself to be sure that it does not stumble into either of these runaway positive feedbacks? Of course thanks to other, negative feedbacks. We ideally do not want to perturb these feedback loops in a way that causes one to dominate and, be it by warming or cooling of the planet, make it inhabitable for us. In fact, these two positive feedbacks mark the upper and the lower boundary for the habitability on our planet and are therefore very important. While greenhouse gases do play a major role in human induced climate issues today, we need CO2 and other greenhouse gases in the atmosphere to counterbalance this cooling. It however takes millions of years for this rescue. Luckily, the greenhouse gas carbon dioxide (CO2) emitted by volcanoes helped recover the Earth into a warmer, more ice-free state. In fact, there is some evidence of several Snowball Earth events in the Earth’s history. This is then called a runaway positive feedback. The critical threshold for this to happen is when the ice from the poles has expanded to about 30 degrees from the equator. This sounds like a scary scenario: a drop in temperature creating too much snow and ice that would at some point spiral out of control to cover our entire planet in snow and ice, turning most of the liquid water available into its solid form. The more ice there is, the more light is reflected, the colder it becomes on the planet and more ice is formed. As a result, the heat of the sun is reflected back into space and temperature on Earth goes down even further, causing more ice to form. Because ice is so bright, it reflects sunlight much more than uncovered surfaces. This causes more ice to form at the poles. A very prominent positive feedback in climate science is the ice-albedo feedback (fig.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |