Science behind global warming

In the latest Friday feature from the University of Huddersfield, chemistry lecturer Dr PAUL ELLIOTT takes a look at the heated issue of global warming

Leaders from around the world are shortly to meet in Copenhagen in an attempt to reach an agreement on legally binding obligations for the reduction of the emissions of carbon dioxide (CO2), the gas responsible for man-made global warming.

It’s the gas that is the by-product from the burning of the fuel in our cars and planes, the coal in our power stations and from a whole host of industries.

“Global warming”, “climate change” and “greenhouse gases” are phrases that are frequently heard in the news but for such an important issue are seldom explained.

So what is global warming, how does it happen and why should we be worried?

The sun is the energy source that warms the Earth’s surface so that we can comfortably live on it.

The Earth is permanently bathed in sunlight. All of the energy that is received by the surface of the Earth is ultimately re-radiated back into space.

Most is immediately reflected back as light but some is absorbed causing it to warm.

That absorbed radiation is later re-radiated in the form of lower energy infra-red radiation or heat.

Certain gases, such as water vapour, in the atmosphere are able to temporarily absorb some of this re-radiated heat energy as it makes its way out to space.

The atmosphere therefore acts as a storage space for heat and so is warmed by these greenhouse gases.

Carbon dioxide is another greenhouse gas absorbing frequencies of this heat radiation that are untouched by the water vapour in the atmosphere. More CO2 in the atmosphere then means more storage space for heat and the atmosphere gets warmer.

For proof of the power of the greenhouse effect, we only need to look at our neighbouring planet, Venus.

Its atmosphere is composed almost entirely of CO2 and consequently its surface temperature is 400C higher than it should be and hot enough to melt lead! Carbon dioxide is naturally released into the atmosphere by volcanoes, natural forest fires and by the organisms on the Earth as a by-product biological energy production.

It gets removed from the atmosphere by plants as they grow but the major route is by it slowly dissolving in the oceans where it eventually precipitates as carbonate minerals.

However, the levels of carbon dioxide released into the atmosphere by the activities of mankind are beyond those that can be dealt with by these “sinks”.

Over the last century this has resulted in a measurable increase in the surface temperature of the Earth, glaciers have retreated as they melt and seasonal ice shelves at the poles have reduced in size.

Global warming has potentially devastating consequences.

Left unchecked, the increased energy in the atmosphere stored by the extra CO2 could lead to more frequent, violent storms and hurricanes, shifts in rainfall patterns with resultant drought and potential mass starvation in affected areas and the extinction and countless species of plants and animals unable to cope with the pace of the climatic changes.

This is why the global community is coming together to try and find solutions and make targets for emission reductions.

It won’t be an easy task and requires multiple solutions.

Our global society is dependent on energy and much of that energy comes from fossil fuels that when burned release CO2.

As a society, we therefore need to change our energy generation technologies to ones that don’t emit CO2 such as wind, wave, tidal, solar and, yes, nuclear.

Industries that produce a lot of CO2 also need to make their processes more energy efficient and need to invest in technologies to capture emitted CO2 so that it doesn’t enter the atmosphere.

But the responsibility is not only on governments and industries.

We as the general public also have our part to play.

We can all do simple things to reduce the energy we use and therefore the CO2 that gets emitted.

For instance, switching the TV off instead of leaving it on standby, getting cavity wall and roof insulation, turning the thermostat down by a degree or two, leaving the car at home and walking, cycling or taking the bus to work.

Some of the main obstacles to agreements on climate change issues for governments and industries come down to economics. It will cost a lot to change to renewable energy sources and to trap emitted CO2.

But the costs further down the line of not acting now will be far, far higher.

The effects of climate change can not be avoided as we are already experiencing them, but by acting together now we can reduce the severity and look forward to a more secure and sustainable world for our children.