Climate change is something we are experiencing and a real issue the Earth is facing. Awareness is being raised and scientists are leading this battle against time. However there are still many questions and loopholes surrounding the area of the study of climate; climate sensitivity being the most uncharted out of them.
So what exactly is climate sensitivity? In simple words, it describes the measure of how the climate of the Earth can become cooler or warmer after there’s a change in the overall climate system. This is directly related to the concentration of CO2 in the atmosphere, explaining how the climate will react to a doubling of this gas. Changes in the climate system are constantly occurring and it is well known that the climate is a dynamic, always changing system, an example of that would be the shift from the glacial period to the Holocene (modern times).
Climate sensitivity is generally studied concentrating on four aspects, the first one is established as the (i) “fast feedback sensitivity” (a feedback being a mechanism that intensifies or diminishes a given starting effect) which mainly deals with natural phenomena such as the change in water vapor of the clouds, in the atmosphere or also the change in sea ice size. As the name indicates, the feedback reacts quickly to any increase or decrease of temperature on Earth. Following this, it is important for the (ii) ice and vegetation albedos to be taken into consideration. Albedo refers to the calculation of how much light that hits a surface is reflected without being absorbed, which is related to and affects the first factor. (iii) Greenhouse gases and (iv) human activity, which is especially important following the Industrial Revolution, are the last two aspects.
Any study of climate sensitivity will provide more accuracy when analysing these four factors as a whole because each individually affects the concentration levels of CO2. From years of various and constant studies, climate scientists agree on a range of an 1.4 – 4.5º C increase in temperature for doubling carbon dioxide. The uncertainty in these calculations extending over a relatively wide range is due to the fact that climate sensitivity cannot in itself be explicitly computed but only estimated through the knowledge we have of the climate of the past and the present. However, this uncertainty means that scientists are not sure whether the already established climate sensitivity will allow us to create future predictions. It currently provides a good basis to control the emissions of CO2 in regulation with the Paris Agreement, keeping an increase in temperature of less than 2ºC. This can allow for more flexible and decisive climate action.
CO2 is one of the prominent gases in the atmosphere (standing at 0.04%), and likewise a member of the greenhouse gases. It is a gas naturally found in the Earth’s atmosphere, but its concentration has increased over the centuries due to human activity. The continuous burning of fossil fuels has led to an escalation of greenhouse gases and predominantly CO2, which accelerates the process of global warming. Contemplating the factors by which climate sensitivity is understood, a lucid picture is painted of how CO2 yields a response from the Earth’s climate, thus if CO2 changes this means the climate system will have to adjust itself to meet these changes. What can actually happen? Climate records are showing us that in the Anthropocene, temperatures are bound to become warmer. The correlation between temperature and concentrations of carbon dioxide point to the fact that an increase of CO2, in a positive feedback mechanism, triggers an increase in temperatures worldwide. Models that have a high “climate sensitivity” predict increases of 4ºC though nothing excludes that this might progressively and dangerously increase in the distant, and even near, future.
It has to be emphasised that the study of the climate is no simple matter, and like any area of science, nonetheless contains unproved hypotheses and uncertainties which yet remain to be studied. This article wants to especially focus on presenting to the general public the concept of climate sensitivity in our understanding of climate change. There are further questions that must be asked… Is “climate sensitivity” the way forward in the knowledge of the climate and deterrence of global warming? What will climate sensitivity be for future generations? If there is something one can be certain of, climate sensitivity allows us to consider the various factors that affect climate and raises a warning to the potential risks we might face if CO2 concentrations continue to increase.
Writer: María Esther Vilar Álvarez
Editors: Omar Alturki/Yara Bawazir
Princeton University. “High end of climate sensitivity in new climate models seen as less plausible.” ScienceDaily. ScienceDaily, 3 March 2021. <www.sciencedaily.com/releases/2021/03/210303161643.htm>.
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Hausfather, Z. (2020, October 5). Explainer: How scientists estimate climate sensitivity. Carbon Brief. https://www.carbonbrief.org/explainer-how-scientists-estimate-climate-sensitivity.