A degree rise in temperature reduces grain production by 10 percent?

The temperature of a site varies periodically from year to year or even from day to day. When we say “yesterday was colder than today,” we are statistically comparing either the lowest temperature for those two days or the average temperature for those two days. And it’s not easy to figure out the average temperature for a day. Traditionally, when we look at the weather forecast in winter, we only care about the minimum temperature, and in summer we only care about the maximum temperature, but we don’t know much about the average temperature each day.
Year to year comparisons of temperatures are even more troublesome. Comparing extreme temperatures is of little significance; comparing average temperatures is more appropriate. Perhaps we can say from short-term memory that Beijing was colder the winter before last. But was the average temperature for the whole of the previous year lower than last year’s? It’s hard to say. It depends on the statistics. When it comes to global climate change, we can’t just judge by physical sensations, but by scientific data.
Unfortunately, scientific data are also incomplete and incomplete. Zhu Kezhen, the former president of Zhejiang University, is a great master in the history of Meteorology in China. His last paper was a preliminary study on Climate Change in China during the Last five Thousand Years, which was published in Acta Archeologica Sinica in 1972. This classic paper is required reading for every student concerned with meteorology. Mr. Zhu Kezhen combined history, phenology, local records and instrumental observations to roughly divide the climate change in the past 5000 years into four warm periods and four cold periods. We’re in the middle of a transition from a cold period to a warm period, so we’re going to get warmer and warmer now, but don’t worry, most of the western Zhou Dynasty or spring and Autumn were warmer than today, and when the temperature peaked it would turn down again and start the next cold period.
Zhu Kezhen’s research is certainly a milestone, but his data, methods and conclusions need to be re-examined by future generations. Before 1900, there were no complete instrumental records in China, and Zhu Kezhen used the methods of history, phenology and local Chronicles to make estimates. Phenology and local records can only provide some clues for us to judge the climate, but do not contain specific data, so many details of Zhu Kezhen’s judgment need to be carefully studied.
Climate is a complex system, which is influenced by local environment, regional environment and global environment. For example, in 1815, the eruption of Mount Tambora in Indonesia sent huge amounts of ash into the air, causing a significant drop in global temperatures in 1816. This year is known in many countries as the year without a summer. Volcanic eruptions are occasional crustal movements that cause short-term global climate changes. These phenomena are not uncommon.
The complexity of meteorological systems is similar to that of economic systems. Our economic activities are as much about the broader global economy as the local economic environment. So long-term global economic trends are hard to predict, and long-term global weather trends are hard to predict. Although there is a lot of evidence that global average temperature is on an upward trajectory, there are so many factors that interfere with this data, including many that we can’t measure and estimate, that we still can’t be 100 percent sure about global warming. Let’s just say it’s a high probability event.
Will climate itself or climate change have an impact on a country’s economic and material life? This proposition seems to be what we often criticize as “geographic environmental determinism”. Three hundred years ago, Montesquieu, in his magnificent treatise on the Spirit of Law, devoted a great deal of time to discussing the influence of climate, environment and physical geography on the laws of a country. Montesquieu’s discussion was later criticized by many scholars.
It is now acknowledged that different countries may vary in geographical location, landform, land area and population, but they are all likely to become countries with developed economy and prosperous people. Norway may be cold, Singapore may be hot, the United States may be flat and Switzerland may be mountainous, but that doesn’t stop them from being among the most developed countries in the world. When we discuss a country’s economic problems, we should pay more attention to its institutions than to its physical geography.
In recent years, some scholars have reconsidered the impact of climate and environmental factors on economic development, because climate will directly or indirectly affect economic activities. Climate differences caused by geographical differences in different countries inevitably affect agricultural production, fresh water supply and tourism development, as well as mortality, crime and conflict, which in turn indirectly affect economic development.
The effects of all these dimensions are different. For mountainous countries, mountains can be both an important tourist resource and a deadly traffic barrier. With its snowy mountains, Switzerland has become a ski destination sought after by people around the world in a way that Nepal cannot. For example, Thailand, which is also close to the tropics, can turn tourism into a pillar industry of the whole country. Nigeria cannot do so.
Beyond that, what are the effects of temperature differences on agriculture? It depends on what agriculture is growing, and agriculture in temperate countries is very different from agriculture in tropical countries. In China’s case, agricultural experts generally agree that low temperatures are good for grain production. For every 1 degree increase in average temperature, food yields will fall by 10 percent, because crops grow less during shorter periods of time in higher temperatures. Whether it’s winter wheat or rice or corn, yields will go down as temperatures rise. China is a big agricultural country, and if the current trend of global warming continues, China’s agriculture will be hit to a certain extent.
A group of academics led by Dell published a paper in 2008 discussing this question. They collated temperature, precipitation and GDP growth rates for 136 countries over half a century, from 1950 to 2003. The bottom line is simple: hot countries tend to be poor, cold countries tend to be rich. This conclusion is consistent with our daily experience. Cold countries, from Northern Europe to Canada, seem to be rich. On the equator, it seems hard to find a more developed country except Singapore.
The next step is to explain the mechanism. Part of the mechanism we’re familiar with is the cumulative increase in temperature, which is bad for both agriculture and industry. In all tropical regions, the weather is not only hot, it is often wet. High humidity has a significant impact on the human body, which can easily lead to fatigue, drowsiness and lack of motivation. As a result, agriculture and industry in the tropics are further affected.

It is not easy for people to adapt to global warming. The faster you adapt, the less it costs; The slower or harder it is to adapt, the higher the cost. And, most importantly, these costs are largely borne by poor countries in the tropics, with less impact on developed countries. …

In addition, Dale found a variable that is often overlooked by economists — the political variable. They found that for every degree rise in temperature, the likelihood of political change in poor countries increased by 2.3 per cent, and the likelihood of an abnormal leadership transition, commonly known as a coup, increased by 3.9 per cent. So the politics of the tropical countries are always unstable, and the politics of the cold countries are relatively stable. By contrast, the political impact of climate on rich, or colder, countries is insignificant.

Climate will have a great impact on the economic level of a country, so how will it affect different countries? The authors used the same model to make predictions. One important variable involved is how long it will take people to adapt to global warming. On the evidence of this winter, adapting to global warming will not be easy. The faster you adapt, the less it costs; The slower or harder you adapt, the higher the cost. Most importantly, these costs are largely borne by poor countries in the tropics, with less impact on developed countries.
In the end, global warming will make poor countries poorer, rich countries remain the same, and the income gap between different countries will widen, which is a very sad thing.
In October 2006, British economist David Stern completed a study assessing the impact of climate change on the UK. The report, now commonly known as the Stern Report, caused great international reaction once it was published. Its conclusion is straightforward: if the world continues to ignore the environmental impact of global warming, mankind will face a global economic crisis and recession similar to the Great Depression in the United States in the 1930s.
Stern called on the world to move quickly to meet national targets for reducing carbon dioxide under the Kyoto Protocol. Stern uses a variety of tools to estimate the benefits of cutting carbon dioxide and the likely costs of not doing so. According to his model, if the world does not take action to reduce emissions, future direct losses from climate change will be equivalent to about 5 per cent of global GDP per year. That’s a staggering number. If indirect losses and wider risks are factored in, losses could rise to 20% or more. But if countries act now to keep greenhouse gas concentrations within the target range quickly, the cost would be about 1% of GDP per year, and even lower later as technology advances. With a cost of 1% and a benefit of at least 5%, governments should know what to do.
The Stern review was opposed by a number of prominent economists, notably Yale’s Nordhaus and Harvard’s Weizmann. In their view, Mr Stern’s plan is too aggressive, aims too high and overstates the risks posed by climate change. Stern could be called a radical; Mr Nordhaus could be described as a moderate. The radicals argue that the pressure to cut emissions is urgent, requiring a multi-pronged approach to forcing emissions down, and that there should be no support for carbon trading. If we don’t use thunder now, it will be too late. Nordhaus said the situation was not nearly as tense as Stern portrayed. It is true that countries should start cutting emissions now, but they can be moderated more gently, using more market-based approaches such as carbon taxes. Wait until people get used to it, then step it up.
The two schools of scholars have their own reasons. Their most fundamental disagreement is the setting of a parameter in the time discount factor. This parameter is a subjective one. Which one is more realistic? This is one of the most controversial and controversial questions in economics.
As it turns out, most environmental economists now seem to be siding with Mr. Nordhaus, who favors modest, gradual cuts in emissions. Greenhouse gas emission reduction is an extremely difficult task that requires coordinated action by all countries in the world. At present, it is quite difficult to promote moderate emission reduction policies, and radical emission reduction policies are basically impossible to implement. But who knows whether it will be too late to adopt only modest emissions-reduction policies, or what the global climate will look like in the future. There’s always a lot of uncertainty ahead of us.

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