Climate change

June 27, 2012, 8:05 pm 

"I have lived in good climate, and it bores the hell out of me.

I like weather better than climate"

John Steinbeck

by Charles Santiapillai and V. Sivakumar

As Mark Twain once commented, "Climate is what we expect, and weather is what we get". Climate and weather are atmospheric phenomena and they differ in time scale. Weather refers to short-term changes (minutes to months) in the atmosphere, while climate is how the atmosphere "behaves" over long periods of time (years to centuries). In other words, climate is a summary of weather patterns in an area over a long period of time. Weather can change from minute-to-minute, hour-to-hour, day-to-day, and season-season. In Melbourne, Australia, sometimes one can experience all four seasons in just one day! On the other hand, climate is an average of weather over space and time. Thus when we discuss climate change, we refer to changes in long-term averages of daily weather.

Five decades ago, Kandy was a much wetter and cooler city than it is today. People carried an umbrella during the day against the rain and used a blanket in the night against the cold. Today, the climate has certainly changed and Kandy is slightly warmer and drier than what it was decades ago. The Red-wattled Lapwing - a typical bird of the low country dry zone – has moved to Peradeniya and today is a resident at the University Campus. 1990s were the hottest decade and 1998 was the warmest year. According to the Intergovernmental Panel on Climate Change (IPCC), global temperature has warmed roughly 0.740C over the past 100 years. More than half of this warming (0.40C) has occurred since 1979.

The Earth’s atmosphere is a thin layer of gases that insulates our planet from extreme temperatures. If you cover a globe with a coat of varnish, then the thickness of the varnish would be about the same as the thickness of the atmosphere in relation to Earth. Thus the atmosphere is a fragile blanket around the Earth composed largely of nitrogen (78%) and oxygen (21%). The remaining 1% is made up of gases such as carbon dioxide, methane, nitrous oxide, ozone and water vapour.

In the 1820s, it was the French mathematician and physicist Joseph Fourier who first indicated that the Earth’s atmosphere might act as an insulator. (Fourier on the belief that his health could be improved by wrapping himself in blankets tripped down the stairs in his house and killed himself!). Later, the Irish Physicist, John Tyndall in 1859 observed through experiments that the abundant atmospheric gases such as nitrogen and oxygen were transparent to radiant heat whereas water vapour, carbon dioxide and methane were not; they absorbed it. Tyndall therefore concluded that the earth’s climate was determined by these imperfectly transparent atmospheric gases, which we refer today as greenhouse gases. It is these gases that regulate our climate.

The atmosphere acts like a glass on a hot-house or greenhouse since it lets through the light rays of the sun (short-wave radiation) much of which is absorbed by the Earth but some is reflected back into space. The natural layer of atmospheric gases absorbs a portion of this reflected long-wave or infrared solar radiation, eventually releasing some of it back into space but forcing much of it back to the Earth. It means that the atmosphere is being heated up from above and below. It is this heat that warms our planet. This is called the Greenhouse Effect. It is a bit like leaving your car in the parking lot on a sunny day. Your car is much hotter inside than outside. It is these heat trapping or greenhouse gases that make our planet a pleasant place to live (at 570F or 140C). In their absence the Earth would be an inhospitable cold planet with a temperature of 00F (or -17.780C).

Unfortunately, today through deforestation, burning of fossil fuels such as coal and gas, we are introducing massive quantities of the greenhouse gas carbon dioxide (CO2) into our fragile atmosphere at rates faster than green plants and oceans can absorb them. The concentration of CO2 in the atmosphere has increased from 270 parts per million (ppm) in 1780 to about 385 ppm today. It is predicted that by 2050, CO2 concentration will reach 500 ppm. It was Sweden’s first Nobel Prize chemist Svante Arrhenius in 1896 showed that the Earth’s temperature would fall if CO2 levels declined. Today, Arrhenius is referred to as the father of climate change. Unfortunately, CO2 is a persistent gas and hence its removal is not easy. Only about one seventh of it can be removed by green plants during photosynthesis.

The term "Global Warming" may not be appropriate since as Freeman Dyson, a onetime Professor of Physics at the Institute for Advanced Study at Princeton, points out, the warming is not global, but local. It is mainly in the Arctic and that too mainly in winter than in summer, and mainly in the night than in the day. The effect of CO2 is important where the air is dry, as in cold areas. Hot desert air may feel dry yet it contains lot of water vapour. That’s why the warming effect of CO2 is felt more where the air is cold and dry – i.e. in the poles and not in the tropics. Although much publicity is given in the media to retreating glaciers, this is not something new or recent. Glaciers have been shrinking for the past 300 years. CO2 is a much maligned gas but its importance cannot be overstated. Plants regard CO2 as food. Using sunlight from the sky and water from roots, plants convert CO2 into oxygen and carbohydrates during photosynthesis. As Freeman Dyson explains, a field of corn growing in full sunlight will use up all the CO2 within a meter of the ground in about 5 minutes. The corn would stop growing if the air was not constantly stirred by convection.

One of the most vital components of our terrestrial ecosystems is the thin layer (5-20 cm) of the topsoil having the highest concentration of organic matter and microorganisms. This is where much of the Earth’s biological activity takes place. According to Freeman Dyson, each year this layer of topsoil absorbs and converts into biomass a certain fraction of the CO2 that we emit into the atmosphere. He feels that the problem of CO2 in the atmosphere is more a result of poor land management than connected to meteorology, and recommends growing more trees, introducing no-till farming, and minimizing the use of the plough.

In plants, the shoot fixes CO2 from the air, and the root extracts mineral nutrients and water from the soil. There is a balance between shoot and root functions. In environments of increased CO2, this balance is altered and hence, the plant would need less leaf area and more root area. Elevated CO2 can stimulate root growth thereby increasing the root/shoot ratio. As Freeman Dyson points out, this means that plants put more of their growth into roots and less into stems and leaves. When plants die and decay, more of the above-ground growth will return to the atmosphere while more of the below-ground will become topsoil. Hence in CO2 enriched environments, plants with increased root/shoot ratio will cause an increased transfer of carbon from the atmosphere into the topsoil.

There are five interconnected reservoirs of CO2 namely, the atmosphere, the surface layer of the oceans, the vegetation on land, the top soil, and fossil fuels. As Freeman Dyson points out, they all interact with each other so strongly that you cannot understand any of them unless you understand all of them. Predictions on climate change are based almost entirely on computer simulations. But according to the Japanese meteorologist Dr Syukuro Manabe, the first to pioneer the use of computers to model global climate change with increasing CO2 levels, computer models are very useful to understand climate, but not a good tool for predicting climate. This is because climate is such a complex phenomenon.

Climate has changed many times before mammals appeared on our planet. Just over a thousand years ago, Vikings settled in Iceland, Greenland and Newfoundland and were able to raise crops and sheep. Romans had vineyards in England as far north as Lincolnshire. Climate change is an irrefutable fact and no one can deny it. We fully believe that we are a part of the problem and our activities and life styles do contribute towards exacerbating an already bad situation. What we are skeptical about is the extent of our influence on it. To think that we alone are responsible for such a change in global climate reflects the same kind of arrogance that led the medieval man to believe that he was the centre of everything and that the sun revolved around him.