About Climate Change

Climate change has hit the headlines of newspapers around the world. We have come to realise that we are responsible for climate change and that it might have significant effects on the way we and people after us are going to live.

What is climate?

How does it work, how do we depend on it and how do we influence it? If we don't understand climate, it will be difficult to take care of it.

The climate of the Earth is described in terms of the temperature at e.g. the Earth's surface, the strength of the winds and ocean currents, the presence of clouds and precipitation, to name a few of its most important features. Obviously these features are all of great importance for life on Earth.

Climate exists because the Earth is receiving energy from the Sun. That energy remains partially trapped within the Earth's atmosphere in the form of heat because gases such as water vapour, carbon dioxide, methane and others are able to absorb heat. Part of the energy is also trapped in the form of motion, i.e. the winds. The more water vapour, carbon dioxide etc. are present in the atmosphere, the more energy is trapped, the higher the temperature on Earth and the stronger the winds.

Is Climate Change really happening? Why is it hitting the headlines now?

Observations clearly show that since pre-industrial times the global mean temperature of the Earth has increased by 0.8 degrees C. In its 2007 report the Intergovernmental Panel for Climate Change (IPCC) states that:

• "There is New and Stronger Evidence that most of the global warming observed over the past 50 years is attributable to human activities".
  The largest contribution to this warming from human activities is due to the emissions of carbon dioxide (CO₂). The initial warming caused by that CO₂ leads to more evaporation hence more water vapour which amplifies the warming. CO₂ is released by burning fossil fuels, by the burning of forests during land clearance; and by certain industrial and resource extraction processes.

Why is it so difficult to predict Climate Change?

Firstly, it is difficult to predict how much fossil fuels will be used in the next century. Since this depends how the world will develop as a whole: how many people there will be on Earth, the level of collaboration between them, the introduction of new technologies, etc. The socio-economic sciences can only give a range of potential scenarios regarding the future. But even if we know exactly how much fossil fuels will be burned, and hence how much CO₂ will enter in the atmosphere, we still have an incomplete understanding of natural processes acting in the climate system. For instance, the way in which CO₂ is absorbed and released by vegetation on land and in the oceans or, more generally, how carbon is transferred from one natural reservoir to another (the carbon cycle), is very complex and we scientists are still uncertain about precisely how this cycle will react to human interference.

Taking the above uncertainties into account, the 2007 report of Intergovernmental Panel on Climate Change concludes:

• "Human influences are expected to continue to change atmospheric composition throughout the 21st century."

• "Emissions of CO₂ due to fossil fuel burning are virtually certain to remain the dominant influence on the trends in atmospheric CO₂ concentration during the 21st century".

• "By 2100 the global mean temperature might increase by 1.1 to 6.4 ºC, compared to 2000". An increase larger than 1.3 ºC is considered to be dangerous and should be avoided.

At present, the global emisisons of CO₂ into the atmosphere are still increasing. In order to stabilise CO₂ concentrations, and hence climate, at safe levels the global emission of CO₂ must start to decline around 2020 and eventually be reduced by 85% by 2050 compared to what they are today.

How can we reduce CO₂ emissions into the atmosphere?

• reducing energy consumption, for example by increasing the efficiency of energy conversion and/or utilisation (including greater use of less energy-intensive economic activities);

• switching to less carbon-intensive fuels, for example natural gas instead of coal;

• increasing the use of renewable energy sources or nuclear energy, each of which emits little or no net CO₂;

• removing CO₂ by enhancing biological absorption capacity in forests and soils;

• capturing and storing CO₂ chemically or physically.