Global warming is a term used to describe a gradual increase in the average temperature of the Earth’s atmosphere and its oceans – a change that is believed to be permanently transforming the Earth’s climate. Climatologists have now agreed that most of global warming is caused by increasing concentrations of greenhouse gases (GHGs) and other anthropogenic (human) activities such as aerosols since the 1950s. Its annual emissions grew by about 80% between 1970 and 2004
In Britain, scientists have studied the possibility of warming of the UK and Europe because of the increasing amount of greenhouse gases, simply because they are more abundant today than ever in the earth’s record.
In my experience, here in Britain, only in the late 1960s, the winters were was so freezing cold that a thick woollen suit with a waistcoat or a sweater inside and a woollen overcoat on top, were not warm enough most of the time. Now, a light woollen or polyester suit and a padded polyester anorak are enough. All woollen overcoats have been shelved.
Britain had frequent heavy snowfalls that brought the traffic to a complete standstill for a few days at a time. These days, severe snowfalls except in the Highlands of Scotland are a rarity. British weather varies year to year, but winters are getting milder and wetter and summers hotter and drier.
Professor Tim Sparks from Coventry University, England said crocuses (small spring-flowering plants) came up 11 days earlier in Kew Gardens in London and swallows, the traditional herald to the end of winter, come from mid-March but there have been sightings in the Isle of Wight as early as mid- February.
Lots of scientific evidence exists to suggest that the climate has changed significantly over the course of the Earth’s history. It has been recognised that over the last 100 years the Earth’s average surface temperature has increased by about 0.8C.
At an IPCC conference in Stockholm in 2013 on the physical science of global warming, scientists agreed and made a landmark report that they are 95% sure that humans have been the “dominant” cause of global warming since the 1950s, producing GHGs, due to the burning of fossil fuels (coal, oil, gas) and deforestation.
Added to this, there is a large amount of methane from permafrost that has raised global warming. The world’s permafrost or permanently frozen land is found mainly in the Polar Regions. It contains more than one third of the current amount of carbon in the atmosphere. When it thaws the underlying organic matter (peat) releases greenhouse gas emissions in the form of methane (second most prevalent GHG) and carbon dioxide.
These findings have been recognized by the national science academies of the major industrialized nations. Climate model projections summarized in their report indicating that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 °C, leading to further global climate change.
Global climate change means more extreme and unpredictable weather across the world as the Earth heats when many places will be hotter, some wetter and others drier.
What is meant by Climate and Weather
Climate models incorporate the physics and chemistry of the atmosphere. Climate is not weather. It is easy to mix up climate with weather. Climate is the description of the average weather we might expect at a given time, usually taken for several decades or longer to average out year to year variability. Variability might be due to a particularly hot summer or very cold winter. Weather means the state of the atmosphere at a particular place and time as regards heat, cloudiness, dryness, Sunshine, wind, rain, humidity and so on, which means the surrounding environment.
The simple way to remember is that climate is what we expect such as cold winters or very hot summers. Weather is what we get such as rain, fog or scorching heat.
The atmosphere of the Earth is the air we breathe in, containing a mixture of gases that create pressure in all the directions. We are unaware of these pressures as our body cavities contain gases that are maintained at the same pressure as outside. For example, though aircraft cabins are pressurised i.e. equivalent to outside air pressure, when the aircraft is descending to lower altitude prior to landing, air must flow back into the middle ears and sinuses in order to equalize the pressure. The opposite happens while climbing up in altitude.
Solar energy consists of radiant light (visible sunlight) and heat (infrared). It does not affect the majority of gases in our atmosphere such as nitrogen, oxygen and argon (gas used in welding), but other gases such as carbon dioxide, methane, nitrous oxide, ozone, and water vapour absorb and emit the Sun’s radiation.
When sunlight hits an object, its infrared energy turns into heat like the warmth you feel while sitting in the Sun. The Sun warms up our planet by heating the land surface, the oceans and the atmosphere. This keeps the Earth warm enough for life to flourish. Almost all life on the Earth (except most bacteria, and fungi e.g. mushrooms that you can grow in the dark in a cellar) require the Sun’s energy. The first life formed or arrived on the Earth (now 4.5 billion years old) 3.5 billion years ago when it cooled down to the point where life could start.
How is the global climate affected
The global climate depends on how much of the Sun’s energy is retained in the land, sea and air globally. There are many factors in the Earth’s atmosphere that affect climate change, such as changes in the Sun’s intensity, volcanic eruptions, heat trapping gases and the amount of solar radiation re-emitted back by the Earth. These are called the primary “drivers” of atmosphere.
Climatologists are definite that climate change with global warming is occurring worldwide, but how much greenhouse gas is contributing to the change is undecided. Besides, there are always sceptics who argue that global warming due to greenhouse gases is a myth. Example: The Wall Street Journal on January 27 2012 ran an Opinion Editorial written by 16 people who denied the evidence of human-induced climate change.
While many sceptics have been denying, many scientists have been involved in studying what has caused global warming. They have come up with the idea that natural events that are known to influence climate change are not enough to cause such an amount of warming and that it can be explained by the inclusion of greenhouse gases in the troposphere (lower atmosphere starting at the Earth’s surface and going up to 7-20 kilometres), emitted by human sources.
It has been noticed that the ozone layer in Earth’s stratosphere (higher atmosphere from 30 to 50 kilometres above the Earth) that forms a protective shield surrounding the entire Earth is thinning out, allowing an increase in harmful ultraviolet-B (UV-B) radiation from solar energy and an increase in the rate of greenhouse warming.
Added to these greenhouse gases are the release by man of gases such as chlorofluorocarbons (CFCs) that are used in refrigerators, air conditioners and in some spray cans to force the contents out of the cans, as well as Chlorocarbons – used in making synthetic rubber, like automobile tyres and tennis shoes. These are considered to break down the Earth’s ozone layer, and alter interactions between the stratosphere and the troposphere and thus cause global warming.
Greenhouse gases in the atmosphere absorb much of this thermal (IR) radiation emitted by the land and ocean following their absorption from the atmosphere. This does not include the immediately reflected portion from the Earth back to space because it does not actually heat the Earth. The exchange of incoming and outgoing solar radiation that warms the Earth is being referred to as the greenhouse effect. In significant quantities these GHGs can force change in the climate system by trapping more and more of the Sun’s warmth and reflecting back to the Earth to cause global warming.
The greenhouse effect is so called because a greenhouse works in much the same way. A normal greenhouse that Europeans keep to grow plants is made of glass roofs and glass walls with a small venting system to allow heat to escape if it becomes too hot.
Incoming solar radiation with ultraviolet (UV) and infrared (IR) rays easily passes through the glass walls and roof. It is easily absorbed by plants and hard surfaces like tables inside. Weaker IR radiation however, has difficulty passing out through the glass walls and roof and is trapped inside and thus warms the greenhouse. The heat helps tropical plants thrive inside a greenhouse, even during a cold winter. It is similar to the heat trapped inside a car when left exposed in scorching heat with its windows rolled up.
One of the main biological impacts of UV radiation on plants is that it reduces their rate of photosynthesis to make food (sugar) by trapping carbon dioxide and releasing oxygen during the process. Plants thus will be starved and lose their ability to grow. This may eventually affect biodiversity and change the structure of an ecosystem.
The writer is based in the UK