The climate was studied before Aristotle
Today, climatology is making rapid headway. When did it start? Credit for the first book on atmospheric phenomena goes to Aristotle (4th century B.C.). It was entitled "Meteorology". However, he mentioned that he borrowed the term from his predecessors. Aristotle cites interesting information about the weather and climate of the past. The word "climate" originates from the Greek "klima", meaning "tilt" (of the Earth's surface towards the Sun's rays). The ancient Greeks realized that the flow of the sun's radiation determines the climate.
Since then climatology has come a long way and become a successful branch of science. The 20th century made a big contribution to it. First, by the beginning of the century scientists had established a global network of hydro-meteorological observatories. Second, they discovered changes in the climate which were more substantial than in previous centuries. Third, a scientific analysis suggested that these changes could be caused by human activity.
Intensified research and awareness of the importance of the problem produced the UN Framework Convention on Climate Change (UNFCCC). Today, scientists from many countries are successfully implementing the global climate program, thereby demonstrating a positive example of globalization.
Russia has always paid due attention to climatology. It started its first meteorological observations in 1725. In 1849, the Normal Observatory was set up in St. Petersburg by decree of Tsar Nicholas I to perform geophysical observations. Its director, Genrikh Wild, was the first to study the link between the sun's activity and the air temperature.
The climate has always been changing
There is no doubt that the climate was changing in the past, too, but its changes never threatened the existence of life on the Earth. Observations by hydro-meteorological stations provide the most authentic information on climate change. To assess the average global air temperature, it is enough to measure the air temperature at ground level and the ocean's surface. But such estimates will still be tentative. Regrettably, nothing is absolutely certain in our study of the climate.
During the 20th century the air temperature at ground level increased by 0.60 ±0.20°C. However, this figure is not very precise. The warmest periods were in 1910-1945 and 1976-2000, while in between there was a mild cool-off. The air temperature increased on all continents, and this phenomenon was dubbed global warming. Radio probes show that the temperature of the bottom 8-km layer of the atmosphere has been increasing at a rate of 0.10°C per decade since the late 1950s. In the meantime, the temperature in the stratosphere has dropped. Therefore, the average temperature of the air mass has remained almost the same. Strictly speaking, we should talk about higher temperatures at the bottom layer rather than about global warming.
Satellite data point to a 10% decrease in snow cover since the late 1960s. Ground surveys show that the ice sheet on rivers and lakes at middle and high altitudes in the Northern Hemisphere disappears a fortnight earlier than before, and that alpine glaciers are retreating in all non-polar regions. The area covered by sea ice in spring and summer has also dwindled by 10% to 15%, and ice has grown thinner. The average sea level has gone up by 0.1-0.2 meters. There is every reason to attribute this to the thermal expansion of seawater and universal melting of land ice.
In the 20th century precipitation grew at a rate of 0.5-1% per decade in the majority of areas in middle and high latitudes of the Northern Hemisphere. In the latter half of the century cases of heavy precipitation became more frequent. Apparently, precipitation in tropical zones of continents increased at a rate of about 0.2-0.3% per decade, and this tendency still prevails. Precipitation subsided in the subtropical areas in the Northern Hemisphere by around 3% per decade. As distinct from the Northern Hemisphere, no systematic changes in precipitation have been registered in the majority of latitude zones in the Southern Hemisphere. This may be attributed to insufficient monitoring of precipitation over the ocean.
Why is the climate variable?
What variations occur in the climate and how well do we understand them? Do we know enough about the climate of past eras, and can we predict how it will change in the future? A statistical analysis of the data received by observations is the main means of tracking climate change. But we will not understand the causes of changes in the climate unless we use the physical and mathematical Global Climate Models (GCM).
Most researchers attribute the growth of the air temperature at the bottom layer of the atmosphere in the 20th century to the greenhouse effect. The atmosphere accumulates greenhouse-gas emissions, which absorb the thermal infrared radiation of the Earth's surface. These emissions are mostly steam, CO2 (carbon dioxide), ozone, methane, and sodium oxide. The aggregate radiation influence depends on the concentration of each greenhouse gas in the atmosphere.
Since 1750, the concentration of CO2 in the air has gone up by 31% due to the burning of organic fuels for economic activity. It has never been so high in the last 420,000 years, or maybe in the last 20 million years. The CO2 concentration has been growing at an unprecedented rate, at least compared with the last 20,000 years.
The cyclical alteration between glacial and interglacial periods is caused by changes in the Earth's orbit around the Sun. This idea gained ground in the 19th century, but Serbian astronomer Milutin Milankovitch turned it into a fundamental theory in the early 20th century. He explained climate change by periodic alterations in the eccentricity of the Earth's orbit and in the tilt and direction of the Earth's axis (precession) as it revolves around the Sun (which happen over a period of 96,000, 41,000, and 23,000 years, respectively). Put together, these cycles generate periodicity in the amount of solar radiation that reaches the Earth's surface in each latitude zone. But conclusions were not easy to make since the continents are not evenly distributed around the globe.
Initially, most meteorologists and geologists were skeptical about this theory. It was accepted only in the 1950s and 1960s, when paleoclimatic data had been accumulated.
Expected anthropogenic changes in the climate
The ability to predict changes in the ocean-air system is limited to two or three weeks. Although this dynamic system is sensitive to minor disturbances, and is therefore unstable, its slowly changing components may be predictable for longer periods. This has been confirmed by the successful modeling of the trends prevailing in the 20th century. Several GCMs were applied to reveal these trends, which were brought about by natural and anthropogenic factors. This success gives rise to the hope that it will be possible to predict future changes in the climate. But to do this, we need to know the scale of future emissions and changes in the concentration of greenhouse gases.
The Intergovernmental Panel on Climate Change (IPCC) has drafted a set of scenarios for emissions into the atmosphere in the 21st century. These scenarios are based on different theories of future development. Global progress is determined by demographic, economic, and technological factors, which in turn influence the intensity of the use of fossil fuels and hence emissions of greenhouse gases and aerosols. Carbon-cycle models make it possible to calculate changes in the concentration of greenhouse gases corresponding to each scenario. The latter are called projections rather than predictions because nobody knows which scenario will take place in reality. Numerous climatic models are applied to each projection of gas concentration in order to generate multiple scenarios, which include temperature, precipitation, and other climatic variables. The GCM-produced scenarios show that in 1990-2100 the average global temperature may increase by 1.50-5.80°C. Such warming has not taken place in the last 10,000 years. The level of the world's oceans may rise by 0.09 to 0.88 meters. It is important to consider that the range of probable changes is very wide because the calculations are based on a large set of possible emissions scenarios. The actions of humankind and the progress of civilization will largely determine which scenario will become a reality. However, there is every reason to believe that anthropogenic factors have played a major role in increasing the temperature in the 20th century by one degree Celsius.
Forecast and consequences of climate change
At present, we can only speak about scenario forecasts, or projections, based on a collection of numerical simulations for different conditions, or on a group of various models. There is a substantial variation in the projections generated by GCMs, which take into account many scenarios of economic performance and demographic aspects. In other words, forecasts of climate change in the 21st century remain vague.
Analysis of the consequences of climate change usually concentrates on the negative aspects - a potential disaster in minor insular nations, or an increase in extreme phenomena. Indeed, we are witnessing a growing number of extreme meteorological and climatic events, which are sometimes very intense. They often have serious environmental and socio-economic consequences. It is enough to recall the recent record temperatures in Europe, which killed thousands of people, and the ensuing widespread forest fires (in France, Italy, Portugal, Spain, and Russia); and monsoon-induced floods in Asia and Africa, which destroyed many homes in Bangladesh, India, Nepal, and Mozambique. This tragic list also includes severe droughts (in Northeast and South Africa more than 20 million were in danger because of a drought); devastating typhoons (China, Japan, and South Korea); and destructive hurricanes (Barbados, Cuba, Jamaica, Mexico, and the U.S.).
Today, scientists are conducting extensive research to determine the potential impact of climate change on a whole range of extreme meteorological events. But so far they have not uncovered any conclusive evidence of either a statistically meaningful increase, or decrease, in the intensity or duration of extreme events, or their connection with global warming. This is one of the most relevant issues for research.
It is believed that the change in the temperature and composition of the atmosphere, and more frequent extreme events require vigorous action at both the political and scientific level. The Kyoto Protocol may be considered a political measure. Scientifically, it is important to consolidate the existing infrastructure, expand monitoring, intensify research, make forecasts less vague, and support climate-oriented services. It is also essential to teach local communities (especially in developing countries) to adapt themselves to the consequences of climate change.
The positive effects of ground-level warming are analyzed much less frequently. Such effects include a reduced need to heat dwellings and prolonged vegetation period, to name but a few.
Growing number of natural disasters
The frequency of natural disasters is uneven. Asia is the obvious leader, accounting for 43% of all calamities and 80% of casualties. Natural disasters may be divided into two groups: hydro-meteorological and geophysical. The former includes avalanches, mud slides, droughts, extreme temperatures, floods, forest and steppe fires, and high winds. Earthquakes and volcanic eruptions belong in the latter group. Data from the World Meteorological Organization (WMO) bear out that hydro-meteorological disasters are more dangerous than geophysical ones (account for 90% of all victims). People are hit the worst by famine-inducing droughts, stormy winds, tsunamis, and floods.
Interestingly, the number of hydro-meteorological disasters was continuously on the upswing in the last decade of the 20th century, whereas geophysical catastrophes remained at almost the same level. Since this decade witnessed substantial climate change, it would be logical to assume that this change brought about an increase in the number of hydro-meteorological disasters, but this assumption has to be buttressed by additional research.
Anthropogenic influence on the climate
Now let us try to see whether we can attenuate the impending change in the climate. What would happen if we could implement an emissions scenario that stabilized their concentration in the atmosphere at a level of between 450 ppm to 1,000 ppm in 100-300 years? To achieve this, we would have to cut down emissions by three to five times in 100-200 years, which is hardly possible. In this scenario, the temperature will continue rising over the next 100-150 years and will eventually stabilize at a level 2-30°C above the current one. The sea level will continue rising for many centuries due to melting ice.
In all scenarios the stabilization will be achieved in two to three centuries. This makes it clear that the measures suggested by the Kyoto Protocol to reduce the greenhouse effect and global warming are absolutely meaningless. They are as effective as an attempt to bail out a big sinking ship. As for drastic cuts in emissions in the future, this problem has not yet been scientifically substantiated.
We do not know what concentration of greenhouse gases in the air is dangerous for humankind, or how cost-effective potential strategies will be. It is important to realize that the Kyoto Protocol has not resolved the problem. It requires thorough scientific analysis and calls for new approaches and revolutionary ideas.
Georgy Gruza, PhD. in physics and math, is professor of the Institute of Global Climate and Ecology at the Russian Academy of Sciences.
