Feedback loops can be used to describe many systems. Negative feedback loops happen when the effects of the system don’t add to the causes of it. The effects of the system can weaken over time if the feedback loop interferes with itself. Positive feedback loops mean that the system feeds into itself, increasing the effects.
One example of a positive feedback loop involves the increase of carbon dioxide levels due to the melting of glaciers. Much of the earth’s CO2 is contained in the ice, and as temperature increases due to an increase of CO2 in the atmosphere, glaciers melt and release even more CO2 which increases the atmospheric temperature further.
Duan et al. studies the relationship between the melting of sea ice and land snow and the increase in CO2. Together they form a positive feedback loop, where the levels of carbon dioxide increase as sea ice and land snow melts, but how much of the CO2 increase is caused by each of them is unknown. To estimate this, they used a model to simulate four scenarios: one where there is both sea ice and land snow, where there is neither sea ice or land snow, where there is only sea ice, and where there is only land snow. For each scenario, they calculated global temperatures and the longwave and shortwave radiation that’s trapped by the CO2.
Through these simulations, they find that sea ice and land snow together increase global warming by about 40%; sea ice alone contributes 17%, while land snow by itself contributes 12%. This study helps demonstrate that there is a tipping point where, if temperatures are high enough, the ice will melt to the point where enough CO2 will be released, causing it to melt completely.