As recent events have shown, even the World Bank would like to understand the trajectory of global warming. There are several ways, but most rely on indicators such as the climate sensitivity. The method of crude, but simple: a doubling of the atmospheric concentration of carbon dioxide average global temperature increases to a certain value.
The Intergovernmental Panel on Climate Change (IPCC) suggests that it is 2-4,5? C with a most likely value of about 3? C. Several studies have shown that the true value is higher, but the next Study, conducted by a large group of scientists and reach millions of years of Earth's history suggests that the IPCC is still more or less right.
|Climate Chronicle (photo JPL / NASA).|
When you add carbon dioxide to the atmosphere temperature increases nonlinearly. IR photon can be absorbed by a molecule of greenhouse gas once. The more gas, the higher the probability of absorption. Therefore, it is considered that every doubling of carbon dioxide (used as the equivalent of the total greenhouse gases in the atmosphere) gives about the same effect.
To calculate this effect, we have to take all the known forces and feedbacks and lay them in the climate model, and then double the carbon dioxide, and see what happens when the system is in equilibrium. That is precisely what the IPCC. But climate models are different, so it did not work one, and range from 2.1 to 4.4 K.
The alternative — try to measure the sensitivity of the climate during periods of major climate changes in the past. Unfortunately, these estimates do not always coincide with the IPCC and also does not always agree with each other. These differences and encourage more collaboration of PALAEOSENS find out what happens.
Part of the problem is caused by a trivial incomplete data. Ice cores that can tell us about climate the last 800 thousand years or so — great chroniclers, and trapped gas bubbles they can make a reasonable estimate of the global atmosphere. But they only show the local temperature. And where there is no ice cores, have to rely on other methods. For example, there is still no satisfactory way to clarify the history of methane — a powerful greenhouse gas.
Another problem lies in the fact that the Earth is a dynamic system. Sometimes it responds to the temperature rise rather quickly — for example, loss of snow cover (which has a cooling effect by reflecting sunlight back into space). Sometimes — gradually. Oceans, for example, act as a giant heat sink that could slow any warming for many centuries. As a result, to find a point of balance is very difficult.
Well, add here the fact that different researchers use different methods to assess climate sensitivity.
Therefore, scientists have re-analyzed published studies based on a single indicator of climate sensitivity and shared a quick response to climate change due to greenhouse gas emissions and long-term response needed to reach equilibrium. The authors believe that the rapid response accounts for about two thirds of the total temperature change and that, as a rule, they occur in the next 100 years.
Through re-analysis clarified. First, the sensitivity of the climate changes over time. In a sense, it was known, has long been noted that the configuration of the continents can affect climate, regardless of the atmospheric and orbital factors. In the last 800 thousand years continents remained more or less in the same place as today, but the climate sensitivity was not the same. Variability is small — within half Kelvin, but it can not be discounted.
Extending the analysis to 65 million years, the authors estimate that the IPCC assessment is true somewhere at 70%. To be more precise, the interval from 2.2 to 4.8 K has a 68-percent level of confidence. 95 percent interval is much wider, and it includes a range of IPCC.
Scientists make alarming conclusion that we'll get to the point where the dinosaurs. While today the concentration of greenhouse gases (due to anthropogenic emissions) is growing much faster than in the Cenozoic (from natural causes). Such a rate of change of the radiation heating the planet has never seen. Predict what will happen, it is very difficult.
The study is published in the journal Nature.
Prepared according to Ars Technica.