Human factors in past, present and future climate change

Global climate change is an important topic of this conference. The related content is divided into three parts, one is the "Daily Theme" report on August 8, the other is the two special seminars on August 6-7, and the third is the comprehensive seminar. Looking at the contents of these reports and their discussions, the hot areas of contemporary earth science related to global climate change include the following aspects.

I. Geological records of climate change

Zhan Sen discussed the large-scale climate system changes caused by global warming and the increase of greenhouse gases. Although it is difficult to quantify and simulate the past changes, it can clearly show the harmonious relationship between ordinary climate change and dynamic changes (such as the change of greenhouse gas capacity in the atmosphere). Peter Barrett discussed the changes of geographical environment from late Cretaceous to early Cenozoic from the perspective of plate tectonic theory reconstruction, and proved the changes of climate and the influence of climate on geographical environment. Hubertus Fischer pointed out that polar ice cores can not only provide high-resolution climate data of two hemispheres, but also provide data of greenhouse gases, suspended particles, solar activity and other most important climate parameters.

Second, climate change prediction

By analyzing the data of the past 50 years, Leneutre bentsen found that the increase of temperature was caused by the increase of greenhouse gases. Considering that the greenhouse gases in the atmosphere have existed on the earth for a long time before the appearance of human beings and cannot be eliminated, we are faced with a serious problem, that is, how to predict the climate change trend of the earth in the next few hundred years and how to balance the climate disorder caused by human beings. From the longer observation data, the climate change is similar to the previous earth climate change, ranging from tens of thousands to hundreds of thousands of years.

Ethan Zhan Sen confirmed the true sensitivity of the monitoring instrument through the known climate change, fully understood how natural and man-made factors interact with climate change, and predicted the future trend of climate change. The fourth assessment report of the Intergovernmental Panel on Climate Change puts forward a brand-new view that the background state of the climate system may play an important role in sudden change. It looks like a sharp change in the region or the whole hemisphere, and it can also turn the climate system into an uncertain system, which is usually triggered in the middle of the cold and warm state during the ice age.

Johnson pointed out that global warming was magnified in the Arctic. In the past 100 years, the temperature increased to twice the global average temperature, and the ice coverage decreased at the rate of 3% ~ 5% per 10, while the annual thick ice coverage decreased at the rate of 7% ~ 10%. In the past few years, the Greenland ice sheet has lost its huge edge, far exceeding its internal accumulation. George Nathan also pointed out that the model of the Intergovernmental Panel on Climate Change did not take into account the potential impact of increased freshwater melting and discharge from the Greenland ice sheet, which added uncertainty to the forecast. Another important issue that has not been considered is the potential increase of carbon dioxide in the Arctic Ocean. Therefore, in the future model prediction, we should consider the influencing factors in this respect and add the revised results.

Third, the relationship between climate change and human activities.

Peter Barrett pointed out in his report that carbon dioxide and temperature have been closely related for the past 650,000 years. The carbon dioxide released by human beings has increased the content of carbon dioxide in the atmosphere, exceeding the level it should have in this period, which will lead to the extreme fluctuation of climate and sea level. From the geological point of view, the earth's climate does have the risk of turning into a warm period at the end of this century.

Peter Schlosser gave the observation conclusion from the Arctic Circle that human actions have seriously affected the climate change, and at the same time, under reasonable assumptions, the climate will change seriously in the near future or even for a long time. In the Arctic Ocean, sea ice and atmospheric system, the latest observation of climate change shows that the Arctic biosphere and other fields of human existence are intrinsically interrelated. The arctic circle system itself has observed the enlarged climate change and its influence, which is reflected in the variability of the internal climate and the relationship between the role of greenhouse gases (including suspended particles) and the role of the climate system on this force.

G.A.Haug pointed out that the comparative data and results of sediments in Lake Maar Lake, a lake in the southeast coast of China, showed that the Holocene intertropical convergence zone data in East Asia and the United States were strikingly similar between 700 and 900, which may be consistent with the decline of the Tang Dynasty in China and the rise of the Mayans in Central America. In addition, by comparing the historical records of Chinese and foreign dynasties, it is found that drought played an important role in the change of dynasties in the past 4000 years.

Fourthly, the external spatial factors of climate change.

Henrik Svensmark reported the influence of cosmic rays on climate change, and thought that the drastic changes of cosmic rays in the Milky Way led to the changes of clouds. Recent experiments show that electrons released by cosmic rays can help to produce suspended particles, thus establishing a large number of concentrated cloud cores. The irregular climate change trend in Antarctica shows the role of clouds in climate change.

Willie Su En replaced geological data with the inherent variability of solar magnetism, weather and climate continuity and climate variability, and introduced the empirical evidence and explanation of climate change in large space and time.

Zhan Sen pointed out that climate change is not only influenced by the internal processes of the climate system, but also by huge external forces, such as the capacity of tracer gas in the atmosphere, solar changes, volcanism, changes in the earth's orbit, and tectonic deformation and orogeny on a longer time scale.

5. How to quickly reduce the emission of carbon dioxide into the atmosphere?

Olaf K. Alstad suggested taking necessary measures to transform the energy system and reduce carbon dioxide emissions. Although it seems impossible to switch from large-scale fossil energy to other energy sources in the short to medium term, we also see the necessity of changing technology to adjust energy structure and demand. IEA's energy forecast shows that carbon dioxide capture and earth storage will play an important role in the fight against climate change and end-use efficiency in the coming decades.

Leneutre bentsen pointed out that although there are many policies that focus on carbon dioxide, the solution to the ozone problem is particularly important. The processing of products should not only consider the reduction of carbon dioxide, but also consider nitric oxide. Nitric oxide produced in some production processes has become a substitute for carbon dioxide, such as wine processing. We must pay enough attention to these greenhouse gases that affect the climate.

(Author He Qingcheng)