What is climate change?

There is now a strong scientific consensus that recent changes in our global climate are almost certainly caused by human activity. Carbon dioxide and other greenhouse gases in the atmosphere, in particular from fossil fuel use and deforestation, are the main contributing factors.

The greenhouse effect is a natural process whereby gases present in the atmosphere, such as water vapour, CO2 and methane, keep the earth warmer than it would otherwise be. Without these gases, the Earth would not be warm enough to sustain the abundance of life around us.

Over the last century the amount of carbon dioxide in our atmosphere has risen (from 280 ppm to nearly 380 ppm), driven in large part by our usage of fossil fuels, but also by other factors that are related to rising population and increasing consumption, such as deforestation.

Although there is still debate as to the magnitude, there is solid evidence that our world is warming (between 0.5 and 1 degree Celsius in the past 100 years). The bulk of the scientific community, led by the Intergovernmental Panel on Climate Change (IPCC) and the United States National Academy of Sciences, has now linked these two phenomena in a likely cause-effect relationship. In early 2007, the scientists of the United Nations’ Intergovernmental Panel on Climate Change re-confirmed the scientific consensus – now with more than 90% certainty – that man-made climate change is underway.

How much more the temperature might rise, and what might happen as a result, is largely governed by the eventual concentration of carbon dioxide in the atmosphere, or stabilisation level. Up to the time of the industrial revolution, this remained at 280 ppm. The IPCC have projected, on the basis of taking no specific action to deal with carbon dioxide emissions, that the atmospheric concentration will continue to rise during the 21st century with stabilization at levels of 1000 ppm or even higher.

Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases:

With regard to changes in snow, ice and frozen ground (including permafrost), there is high confidence that natural systems are affected.
Based on growing evidence, there is high confidence that the following effects on hydrological systems are occurring:
- Increased run-off and earlier spring peak discharge in many glacier- and snow-fed rivers;
- Warming of lakes and rivers in many regions, with effects on thermal structure and water quality
There is very high confidence, based on more evidence from a wider range of species, that recent warming is strongly affecting terrestrial biological systems.
There is high confidence, based on substantial new evidence, that observed changes in marine and freshwater biological systems are associated with rising water temperatures, as well as related changes in ice cover, salinity, oxygen levels and circulation.
Based on satellite observations since the early 1980s, there is high confidence that there has been a trend in many regions towards earlier ‘greening' of vegetation in the spring linked to longer thermal growing seasons due to recent warming.

Inertia is an inherent characteristic of the climate system, with CO2 concentration, temperature and sea level continuing to rise for hundreds of years after emissions have been reduced. Therefore some aspects of man-made climate change may be slow to appear.

Tackling climate change

The scientific evidence is now overwhelming: climate change is a serious global threat, and it demands an urgent global response. Using the results from formal economic models, the Stern Review estimates that if we don’t act, the overall costs and risks of climate change will be equivalent to losing at least 5% of global GDP each year, now and forever. If a wider range of risks and impacts is taken into account, the estimates of damage could rise to 20% of GDP or more.

In contrast, the costs of action - reducing greenhouse gas emissions to avoid the worst impacts of climate change - can be limited to around 1% of global GDP each year. The investment that takes place in the next 10-20 years will have a profound effect on the climate in the second half of this century and in the next. Our actions now and over the coming decades could create risks of major disruption to economic and social activity, on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century. And it will be difficult or impossible to reverse these changes.

So prompt and strong action is clearly warranted. Because climate change is a global problem, the response to it must be international. It must be based on a shared vision of long-term goals and agreement on frameworks that will accelerate action over the next decade, and it must build on mutually reinforcing approaches at national, regional and international level.

Starting to reduce our emissions now is an essential first step, eventually leading to a much lower final atmospheric stabilisation of CO2. But major changes in our energy infrastructure will be required. A level of stabilisation of less than 500 ppm will be very difficult to achieve, as it requires a sharp downward turn in emissions before 2020. Stabilisation at a somewhat higher level would be more achievable as it allows a timeframe in which significant change in our energy infrastructure could take place.

A reduction of 6-7 Gt of CO2 (22 Gt CO2) emissions per year by 2050 compared to the 'business as usual' scenarios illustrated would place us on a 550 ppm trajectory rather than 1000 ppm CO2, but a step-change (r)evolution in our energy infrastructure would be required, utilising resources and technologies such as:

A further shift to natural gas
In power generation, a typical coal fired facility will produce 950+ grams of CO2 per kWh of electricity produced. By contrast, a combined cycle gas turbine (CCGT) will produce only 450 grams of CO2 per kWh. The difference is due to combustion efficiency achievable with gas and the higher energy content of gas.
Nuclear energy
Nuclear energy offers a clear zero CO2 emissions alternative for power generation, although public acceptance of this technology remains an issue.
Alternative energies
For example, 300,000 MW wind turbines, built in place of the equivalent generation capacity from coal, would save 1 Gt per annum of CO2 emissions.
Bio-products
Advanced bio-fuels such as Ligno-cellulosic ethanol offer the prospect of a liquid transport fuel with very low or even zero net CO2 emissions.
CO2 capture and storage
Fitting out the equivalent of today’s coal fired generating capacity with CO2 capture and storage would reduce CO2 emissions by 1 Gt by 2050.
Advanced vehicle technologies
By 2050 there could be as many as 2 billion vehicles in the world. If they all utilised, high efficiency drive trains such as we see in hybrid vehicles just appearing on the market today, emissions could be lower by 1 Gt CO2 in 2050. New vehicle fuels such as hydrogen offer a very different solution to sustainable mobility.
Other energy efficiency measures

The reality of the issue

In early 2007, the European Union declared it’s intention of a 20% reduction of its greenhouse gas emissions by 2020, and a 30% reduction if developing countries also contributed - an important milestone on the way to its stated goal of limiting global warming to 2 degrees Celcius.

An illustrative calculation of what might be needed to achieve this outcome shows that a wide range of measures are needed to meet growing energy needs and address the issue of climate change. Today the EU-25 uses about 70 ExaJoules (EJ) of primary energy and as a result emits about 1.3 Gigatonnes (GT) of CO2 to the atmosphere (about one sixth of the global total). Energy demand across the EU-25 can be expected to grow over the next 20 years, with particular pressure coming from the expanding economies of the accession countries. With energy efficiency measures in place, this might be limited to an overall increase of 6%. Reducing CO2 emissions by 20% in this context (to 1 GT of CO2) would require all of the following by 2025:

Nearly a third of all coal fired power generation capacity will need to utilise CO2 capture and storage technology, which means this technology must be commercialised by the end of this decade. Today it is principally a research and development activity.
Natural gas use needs to grow by some 50%, with the emphasis on power generation.
Nuclear power remains a key zero CO2 energy source (growing by some 10% over the period), yet the future of this technology is unclear in many parts of the EU.
Renewable energy (wind and solar) will need to grow substantially, with wind power alone being some 10-20 times today’s levels across the EU-25. This means a consistent approach across the EU to renewables development policy.
Distributed solar power (e.g. on rooftops etc.) provides 5% of electricity needs.
With the call on mobility continuing to grow, transport must change considerably. Average on-the-road vehicle efficiency will need to improve by 50% and a zero emission alternative (e.g. advanced bio-fuels or hydrogen from renewables) must have a strong foothold in the sector (approaching 10% on-the-road).

This example is illustrative and clearly challenging, but demonstrates the need for a wide range of technologies to be deployed over the coming decades. Much of this technology is available today.

Shell is already involved in developing and deploying such technologies:

More information

Publications from the Intergovernmental Panel on Climate Change (IPCC) - opens in new window
The Stern Review Executive Summary (PDF, size 310 Kb) - opens in new window
Three reports from the World Business Council for Sustainable Development:
- “Energy and Climate Change: Facts and Trends to 2050” (PDF, size 1.9Mb) - opens in new window a 2004 publication by the World Business Council for Sustainable Development - opens in new window
- Pathways to 2050 - Energy & Climate Change (PDF, size 2.9Mb) - opens in new window which builds on Fact and Trends to 2050, and provides a more detailed overview of potential pathways to reducing CO2 emissions, showing the scale and complexity of change needed, as well as the progress that has to be made through to 2050.
- Policy Directions to 2050: A business contribution to the dialogues on cooperative action - opens in new window asserts that the only way to combat climate change is through decisive, concerted and sustained actions between governments, businesses and consumers.

→ Shell Sustainability Report 2006

Visit the online Shell Sustainability Report 2006 and discover what we say about climate change - opens in new window.

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