As recent events have shown, even the world Bank want to understand the trajectory of global warming. There are several ways, but most rely on such factors as the climate sensitivity. Method rough, and simple: a doubling of the atmospheric concentration of carbon dioxide, the average temperature on the planet increases to a certain value.

The intergovernmental panel on climate change (IPCC) believes that it is 2-4,5 C, with a most likely value of about 3 C. a Number of studies have shown that is true to a higher value, but another study, carried out by a large group of scientists and engulfed millions of years of Earth's history, suggests that the IPCC is still more or less right.

Adding carbon dioxide to the atmosphere temperatures are rising non-linear way. IR photon can be absorbed by the molecules of the greenhouse gas only once. The more of these gases, the higher the probability of absorption. Therefore, it is considered that each doubling of carbon dioxide concentrations (it is used as an equivalent of the total content of greenhouse gases in the atmosphere) gives approximately the same effect.

To calculate this effect, it is necessary to take all the known forces and feedback and establish them in a climate model, then a doubling of carbon dioxide and see what happens when the system reaches equilibrium. That was precisely what the IPCC. But climate models are different, so not a single value, and range from 2.1 to 4.4 K.

The alternative is to try to measure the sensitivity of the climate in periods of large climate changes in the past. Unfortunately, these assessments do not always coincide with the IPCC and besides it is not always agree with each other. These differences and encouraged greater collaboration PALAEOSENS to find out what happens.

Part of the problem caused by banal incomplete data. The ice cores that can tell us about the climate of the last 800 thousand years or so, is a great chroniclers, and captured gas bubbles make a reasonable estimate of the global atmosphere. But they 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 clear the history of methane is a powerful greenhouse gas.

Another problem is that the Earth is a dynamic system. Sometimes it reacts to temperature rise quickly - for example, loss of snow cover (which has a cooling effect by reflecting sunlight back into space). Sometimes gradually. The oceans, for example, act as a giant radiator that can slow down any warming for many centuries. The result is to find a balance point is very difficult.

Well, we add here the fact that different researchers use different methods of estimating climate sensitivity.

Therefore, scientists re-analyzed already published studies on the basis of a single indicator of climate sensitivity and divided quick response to climate change through the release of greenhouse gases and long-term response required to achieve equilibrium. The authors believe that rapid response accounts for about two thirds of the total temperature change and that, as a rule, they come within 100 years.

Due to the re-analysis something cleared up. First, the sensitivity of climate change with time. In a sense, it was known: it has long been observed that the configuration of the continents can affect climate, regardless of the atmospheric and space factors. In the last 800 thousand years continents remained more or less the same places that today, however, the climate sensitivity was not the same. Variability small - within one and a half degrees Kelvin, but it cannot be discounted.

Extending the analysis to 65 million years, the authors estimated that the IPCC assessment is correct is about 70%. To be more precise, the interval from 2.2 to 4.8 It has a 68-percent level of confidence. 95% interval is much wider, but it includes the range of the IPCC.

Scientists make the disturbing conclusion that we will return to the point at which the dinosaurs. As of today, the concentration of greenhouse gases (due to anthropogenic emissions) is growing much faster than in the Cenozoic era (for natural reasons). This rate of change in radiative heating of the planet did not know. To predict what awaits us, very difficult.

The study is published in the journal Nature.

Prepared according to Ars Technica.