Why did 20 17 become the hottest year in history?

The main factor of temperature rise is human activities, followed by the appearance of La Nina phenomenon in 20 17 years, which also led to the gradual increase of temperature. Therefore, there are two main reasons for making 20 17 the hottest year in history:

Long-term effects of human activities

La Nina phenomenon?

According to the British Daily Mail 65438+ 10/8, a new study found that 20 17 became the hottest year without El Nino in history.

In the year of El Nino, the prevailing wind direction will change, which will lead to a large area of water temperature increase in the Pacific Ocean, which in turn will lead to a global temperature increase. Compared with the El Nino year, the temperature rose slightly in 20 16, but it rose the most in 20 17, making it the hottest year in history.

Scientists say that in the past 150 years, the most important factor of temperature rise is human activities. These include burning fossil fuels, which will release a lot of heat-absorbing greenhouse gases into the atmosphere. Scientists say that human-induced climate change is beyond the power of nature itself. According to the temperature record of 20 17, world leaders should pay attention to the scale and urgency of the risks brought by climate change.

Experts from the Hadley Center of the British National Weather Service and the Climate Research Center of the University of East Anglia participated in this research and produced the "Hadcrut4" data set to assess global temperature. The results show that the temperature level in 20 17 years is1981℃ (1.8 f) higher than that in 1850- 1900 years ago. 20 17 became the hottest year in history.

A series of international analysis data of National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (Nasa) also show that 20 17 has become the hottest year in history. The temperature in 20 17 years exceeded the highest temperature recorded in 20 16 years, and some data were higher than those analyzed in 20 15 years.

El Nino occurred at 20 15 and 20 16, which is a natural phenomenon in the Pacific Ocean. In addition to man-made global warming, El Nino will also raise the temperature.

Dr Colin Morice of the Hadley Center of the British National Weather Service said that the global temperature data measured by the center in 20 17 were consistent with those measured by other centers in the world. Without the influence of El Nino, 20 17 became the hottest year in three years and the hottest year since 1850. 20 15, 20 16 and 20 17 became the hottest three years. In addition to the persistent greenhouse gas emissions, 20 15 and 20 16 were also affected by the strong El Ni? o phenomenon. However, 20 17 is the most noteworthy, because the El Ni? o phenomenon did not appear that year, and the La Ni? a phenomenon appeared, but the temperature continued to rise.

The persistent El Nino phenomenon in 20 15-20 16 years increased the annual average temperature in 20 16 years by about 0.2℃(0.36℉), which was about 1850- 1900.

The forecast of the global annual average temperature in 20 17 by the British Meteorological Office shows that the global average temperature in 20 17 is expected to exceed the long-term average level and remain between 0.32℃(0.57℉) and 0.56℃( 1℉). According to the average of three global temperature data sets, the temporary data of 20 17 years is 0.42℃(0.75℉) higher than the long-term average, which is within the forecast range. Correct analysis of the forecast at the end of 20 16. 20 17 will be one of the hottest years in history.

"HadCRUT4" global temperature data set is compiled from thousands of global temperature measurement data. The regional change of temperature itself provides reference information for understanding the causes of warming mechanism, so as to deal with the continuous accumulation of greenhouse gases in the atmosphere. Professor Tim Osborne, research director of the Climate Research Department of the University of East Anglia, added that it is necessary not only to analyze the global average temperature data, but also to explain the geographical pattern of climate warming. At first, the understanding of climate physics was that the greater the warming of the land and the Arctic, the smaller the sub-polar warming. Now, this result has been observed.

The World Meteorological Organization (WMO) has compiled five international data sets and said that the temperature has been rising for a long time. Petteri Taalas, Secretary General of the World Meteorological Organization, said that the long-term temperature change trend is more important than the ranking of individual years, and this trend will rise. In the hottest year of 18 recorded, 17 occurred in this century, but the degree of warming in recent three years is an exception. The warming of the Arctic is particularly significant, which will have a far-reaching impact on the sea level and weather conditions in other parts of the world.

It is also said that the temperature rise of 20 17 directly leads to extreme weather in many countries around the world. The United States experienced the worst year affected by extreme weather and climate disasters, while other countries also experienced economic slowdown or negative growth due to tropical cyclones, floods and droughts.

US President Trump announced that the United States plans to withdraw from the Paris Agreement, which is the world's first comprehensive agreement on reducing greenhouse gas emissions, which will make the United States the only country that has not signed the agreement.

Bob Ward, an expert on climate change at the London School of Economics and Political Science, said that although he did not participate in this research, with the increase of temperature, extreme weather will appear all over the world, such as hurricanes in the Caribbean and the United States. All countries will face the impact of climate change. This year, the government will begin to assess the gap between reducing greenhouse gas emissions and the targets of the Paris Agreement. World leaders should pay attention to the magnitude and urgency of global climate change risks caused by population, wealth and climate change according to the recorded temperature data.

Because the observation data can't cover all regions of the world, especially polar regions, and the measuring equipment used to generate data sets has limitations, the calculation results are full of uncertainty. The available data for evaluating the differences mainly come from sporadic data in polar regions.