What is climate sensitivity

You could, however, use our results to assess whether a climate model has a sensitivity that is within our independently constrained range. Ultimately, it tells us that while human-made climate change is and will continue to be a problem, our actions as a society can change that trajectory. We explored some of these alternative choices and that broadens the uncertainty a little, but basically, we estimate that there is about a one-in-six chance that it was less than the low end, and one-in-six that it was higher than the high end.

The climate sensitivity tells us what we can expect in terms of temperature — between another 1 or 2 degrees Celsius 1. Credit: NASA's Goddard Institute for Space Studies Recently, an international research team published a comprehensive review in the journal Reviews of Geophysics on our state of understanding of Earth's "climate sensitivity," a key measure of how much our climate will change as greenhouse gas emissions increase. What exactly is climate sensitivity and why is it important to know its true value?

Your team was able to narrow the range of estimates of Earth's climate sensitivity by more than 43 percent, from the previously accepted range of 1. Why is it important for scientists to narrow this range of uncertainty? What does it mean in practical terms to be able to reduce uncertainties in measuring climate sensitivity?

How can better estimates of climate sensitivity impact policy decisions? Why has it been so difficult over the past 40 years to narrow this range? What made this new estimate possible? What types of evidence did the team consider in reaching its conclusions? Armour, K. Energy budget constraints on climate sensitivity in light of inconstant climate feedbacks.

Hartmann, D. Southern Ocean warming delayed by circumpolar upwelling and equatorward transport. Parkinson, C. A y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic. Lenssen, N. Gistemp, T. Forster, P. Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models.

The dependence of radiative forcing and feedback on evolving patterns of surface temperature change in climate models. Austin, R. Retrieval of ice cloud microphysical parameters using the CloudSat millimeter-wave radar and temperature.

Deng, M. Download references. You can also search for this author in PubMed Google Scholar. Correspondence to Trude Storelvmo. Dots are placed at the middle of each year interval, for the total cloud feedback black and separated into the cloud amount feedback yellow , the cloud altitude feedback red and the cloud optical depth feedback blue.

Source data. The autumn MAM grid-box average of cloud water amount and temperature profiles red lines for the pre-industrial control simulation a , the first 15 years b , and the last 15 years c , of the year simulation with quadrupling of CO 2.

The ice fraction is light blue and the liquid fraction in dark blue. Same as Extended Data Fig. Grid-box average cloud water amounts including snow and rain, and temperature profiles for the pre-industrial control simulation and from satellite observations see Methods for Summer a , b , Fall c , d , Winter e , f , and Spring g , h. Note different x-axes. Reprints and Permissions. Bjordal, J. Download citation. For many years, estimates have put climate sensitivity somewhere between 1.

This range has remained stubbornly wide, despite many individual studies claiming to narrow it. However, recent work combining multiple lines of evidence may have helped modestly narrow this range.

Here, Carbon Brief examines studies of climate sensitivity published over the past two decades. While narrowing the range of sensitivity will not change the need for rapid decarbonisation, it may help policymakers fine-tune their plans for the future. Climate sensitivity refers to the amount of global surface warming that will occur in response to a doubling of atmospheric CO2 concentrations compared to pre-industrial levels.

CO2 has increased from its pre-industrial level of parts per million ppm to around ppm today. Without actions to reduce emissions concentrations are likely to reach ppm — double pre-industrial levels — around the year There are three main measures of climate sensitivity that scientists use. The first is equilibrium climate sensitivity ECS. For example, the extra heat trapped by a doubling of CO2 will take decades to disperse down through the deep ocean.

ECS is the amount of warming that will occur once all these processes have reached equilibrium. The second is transient climate response TCR. TCR more closely matches the way the CO2 concentration has changed in the past. It differs from ECS because the distribution of heat between the atmosphere and oceans will not yet have reached equilibrium.

A third way of looking at climate sensitivity, Earth system sensitivity ESS , includes very long-term Earth system feedbacks, such as changes in ice sheets or changes in the distribution of vegetative cover. The wide range of estimates of climate sensitivity is driven by uncertainties in climate feedbacks , including how water vapour, clouds, surface reflectivity and other factors will change as the Earth warms.

Climate feedbacks are processes that may amplify positive feedbacks or diminish negative feedbacks the effect of warming from increased CO2 concentrations or other climate forcings — factors that initially drive changes in the climate.

Simple physics shows the world will warm by a bit more than 1C once CO2 doubles, if feedbacks are not taken into account. Water vapour — itself a powerful greenhouse gas — is the single largest and one of the best-understood climate feedbacks.

As the world warms, the amount of water vapour in the atmosphere is expected to increase and, therefore, so too will the greenhouse effect. Measurements from satellites confirm that water vapour concentrations have been increasing in step with temperatures in the atmosphere over the past few decades.

A warmer and wetter atmosphere will also affect cloud cover. However, it is much more uncertain how changes in cloud cover will influence climate sensitivity. An increase in low-altitude clouds would tend to offset some warming by reflecting more sunlight back to space, whereas an increase in the height of high-altitude clouds would trap extra heat.

Meanwhile a shift in sun-blocking clouds from the tropics towards the poles, where the incoming sunlight is less intense, would decrease their power to block sunlight. All this means the global net effect of cloud feedbacks is complex and hard for scientists to model precisely. A warming world will also have less ice and snow cover. Nearly 40 years later, the best estimate of sensitivity is largely the same.

This has led some to question why there has been so little progress on estimating climate sensitivity. He tells Carbon Brief:. So their estimate of uncertainty was, in my opinion, way, way too small. Animals that have specific ecological niches will struggle as those niches rapidly change or move due to climate change. This will affect a range of animals, including, but not limited to:. Other animals will be impacted by their food sources moving or disappearing, which has a profound impact on survival.

Songbirds are already adjusting their migration routes to deal with climate-changed landscapes, in some cases having to fly further for food or water, as well as deal with more extreme weather events and wildfires, which is presumed to be behind recent unprecedented mass die-off events. The distribution and abundance of plants will be affected by climate change on multiple levels. In areas affected by drought, some plants won't have enough water to grow and reproduces. Others, like the iconic Joshua Tree, won't be able to adapt quickly enough to changing conditions.

A more volatile and destructive weather system has tremendous impact on human lives and activities. Those people with fewer resources to move or rebuild will suffer at much greater rates than those people in richer countries or who have personal wealth. That means that the majority of the negative effects of climate change — loss of life, as well as homes, businesses, and basic resources like clean water — have already and will continue to be borne by those with the least.

This holds true even within countries with higher per-capita incomes. Climate change effects will also be costly. Estimates of the costs of climate change vary depending on what is included: Some studies look at the costs of increasing disasters on global trade alone, while others look at the cost of disruption to "free" ecosystem services—the work that a wetland does in filtering water, for example.

Climate sensitivity currently has a wide range: that 2 to 4. People will die earlier than they would have otherwise due to climate change effects. Indigenous communities will be less able to hunt, gather, and engage in traditional practices in ecosystems that are unable to support the plants and animals traditionally found there. We are already past the time when making more significant reductions in CO2 could avoid significant warming. Lindsey, Rebecca.

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Levy, Barry and Patz, Johnathan. Jay, A, et al. Global Climate Research Program , , pp. Hope, Chris. Herring, David and Lindsey, Rebecca. Actively scan device characteristics for identification.

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