Swiss climate scientists assessed the impact of human factors on climate change by the method of evaluation of the energy balance of the Earth — the amount of "incoming" and "outgoing" heat — and confirmed that a temperature rise in the second half of the 20th century has led primarily by human activities, the article says in the journal Nature Geoscience.
"Our results show that with an extremely high probability of 74% (+ / -12%) of the observed warming since 1950 was due to human influence, and less than 26% (+ / -12%) — natural fluctuations in temperature" — write Marcus Huber (Markus) and Reto Knutti (Reto Knutti) from the Institute of climate science and the atmosphere of the Federal Institute of Technology in Zurich.
Scientists note that there is still evidence of anthropogenic nature of global warming, mainly based on the difference between spatial and temporal characteristics of the temperature rise caused by natural factors and human activities. The authors used an alternative and more rigorous method — the energy balance of the planet, that is, the ratio of energy that the Earth receives from the Sun and reflects back.
This is not the first such study — Climate scientists from the University of California at Berkeley (USA) and their colleagues from other educational and research centers in the world held a large-scale study of BEST, which has demonstrated the reality of human impact on the climate by analyzing the changes in temperature at the surface of the Earth. According to their estimates, the average temperature on the planet for the last 50 years have increased by 0.9 degrees Celsius.
Huber and Knutti collected statistics on variations of solar radiation in the period from 1850 to the present. They integrated the information into climate model Bern2.5D and monitor changes in the absorption of heat the planet itself, as well as the amount of energy that the Earth stands out in space. Using these data, scientists have tried to separate the anthropogenic drivers of climate change from the action of natural forces.
In general, the simulation results for the years 1950-2004 in good agreement with the actual changes in the average temperature, and other factors of climate change. Scientists have analyzed the results of the model for each year and have tried to calculate the "contribution" of each of the natural and anthropogenic factors affecting the energy budget of the planet.
The most influential factor was the power fluctuations in solar radiation, followed by the growth of greenhouse gas emissions and increasing the concentration of aerosols in the atmosphere. "Traces" of climate change are clearly visible — in the last half century the average temperature of the Earth has increased by 0.55 degrees Celsius, which is very close to the actual 0.51 degrees. Increasing concentrations of greenhouse gases corresponds to the increase in average temperature by 0.85 degrees Celsius, but their impact was mitigated effects of aerosols, which reduced the rate by 0.45 degrees Celsius.
According to scientists, human-made greenhouse gases are the main cause of warming in the past 50 years. On the other hand, natural factors neutralize each other — their combined strength was close to zero. Fluctuations not related to climate change, were only a quarter (26%) or six (18%) of the total increase in temperature over the last 50 100 years. Moreover, the effect of carbon dioxide was extremely durable — climate "traces" of elevated CO2 will be visible even after a thousand years. Scientists believe that this highlights the need for a primary fight for the reduction of carbon dioxide emissions. / / RIA Novosti