Is it warming or cooling?

Since the 1960s, many meteorologists have become increasingly interested in using computers to model weather processes. There is a growing recognition that the Earth's environment is an extremely complex structure,

and that small changes in the initial state can bring about large, random changes in future climate. There's a famous saying going around: "A butterfly flapping its wings in Brazil can start a tornado in Texas."

However, the warming trend since the 1930s has not been sustained. In the early 1960s, meteorologists talked openly about how, while global temperatures had been warming until the 1940s, they had recently been falling.

Measured at the time, carbon dioxide was steadily increasing, but temperatures in those years were falling, which could not be explained by the "greenhouse effect" of carbon dioxide. Meteorologists can only call it "a curious puzzle."

Indeed, since the mid-1940s, and especially since the 1960s, there has been a marked cooling in the Arctic and the high latitudes near the North Pole, and these changes are clearly reflected in meteorological observations, biological ecology, and many aspects of nature.

In the 1960s, the extent of freezing in the North Atlantic increased, creating cold temperatures not seen in decades across large areas of Europe, the Americas, and Asia. Due to the freezing of the North Atlantic Ocean, the link between Greenland and Iceland was once a natural "ice land" on which polar bears could travel freely.

In the Americas, the growing season of plants in the United States is half a month shorter than it was in the 1940s. Phenological observations in Japan show that the beginning of cherry blossom in Japan has been delayed since the 1950s.

Will the cooling trend continue? How long will it last? In this regard, the cooling theorists have made various speculations: some people estimate that the cooling trend in recent years may be a period of several decades,

so the cooling trend may continue for about 20 to 30 years, and some people estimate that the climate in the next 20 to 30 years may be colder than the current climate, but there will be no extreme situation.

In addition, some people believe that the cooling of the climate since the 1960s is a harbinger of the arrival of the "Little Ice Age", and that the world's climate will enter an ice age from the next century.

While scientists can't agree on whether the world is warming or cooling, they do agree that efforts to understand how the climate system works should be redoubled in the first place.

It's getting warmer?

In 1986, the Climate Research Unit, established by the UK government at the University of East Anglia, completed the first reliable and comprehensive global analysis of mean surface temperatures.

They found that in 134 years of record, the three warmest years all occurred in the 1980s. Hansen and a collaborator in the research department ran the analysis in a different way and got the same results. That's right - unprecedented warming is on its way.

The fuse was lit in the summer of 1988. The worst series of heat waves and droughts since the Great Dust Bowl of the 1930s ravaged many parts of the United States. The cover articles of newsmagazines, the headlines of television newscasts,

and countless newspaper columns provided the public with vivid images of parched fields, sizzling cities, "superhurricanes," and the worst forest fires of the 20th century.

The reporters asked: Is all this caused by the greenhouse effect? A growing number of meteorologists are saying that a long-term warming trend is under way, and they strongly suspect that the greenhouse effect is the culprit.

Media coverage of the news is so widespread that, according to a 1989 poll, 79 percent of Americans remembered having heard or read about the "greenhouse effect," a huge jump from 38 percent in 1981.

In response to all these pressures, in 1988, the World Meteorological Organization and other United Nations environmental agencies established the Intergovernmental Panel on Climate Change (IPCC).

Unlike previous panels of climate experts, the IPCC is largely made up of government representatives from around the world - people with strong ties to national laboratories, weather bureaus, scientific agencies and the like.

It is neither strictly a scientific institution nor strictly a political body, but a unique hybrid. The agency's primary mission is to assess the current state of scientific knowledge on climate change, its potential impacts on society and the economy, and possible countermeasures on how to adapt to and mitigate climate change.