Fossil fuels, greenhouse gases ,climate and energy prospects to 2020–2030
Humanity’s emissions of the main greenhouse gas, carbon dioxide (CO2), from these fuels have increased enormously since 1850. There have also been significant additional contributions from emissions of methane and other greenhouse gases.
Causes of climate change
What are the causes of climate change?
The surface temperature of the Earth establishes itself at an equilibrium level where the incoming energy from the Sun balances the outgoing infrared energy re-radiated from the surface back into space.
If the Earth had no atmosphere its surface temperature would be minus
18 °C, but its atmosphere includes ‘greenhouse gases’. The natural ‘greenhouse effect’ that these gases cause is essential in maintaining the Earth’s surface temperature at a level suitable for life – around 15 °C.
Scientists estimate (IPCC, 2007a) that these human-induced emissions caused a rise in the Earth’s global mean surface temperature of approximately 0.7 °C between 1950 and 2005, as you can see from the figure above. If emissions are not curbed it is estimated that the surface temperature will continue to rise by between 1.4 and 5.8 °C by the end of the twenty-first century.
Such rises would increase the frequency of climatic extremes - floods or droughts, causing serious disruptions to agriculture and natural ecosystems. The thermal expansion of the world’s oceans could mean sea levels rising by around 0.5 m by the end of the century, which could inundate some low-lying areas. Beyond 2100, or perhaps before, much greater sea level rises could occur if major Antarctic ice sheets were to melt. This threat of such global climate changes is one of the main reasons why there is a growing consensus on the need to reduce greenhouse gas emissions.
So what should we do to reduce emissions?
Climate change experts advise that global mean temperature rises by 2050 should not exceed 2 °C above pre-industrial levels, and that to achieve this global carbon emissions will need to be reduced by approximately 80%. This implies that global CO2 emissions need to peak almost immediately and then fall sharply over the course of the rest of this century (Allen et al., 2009). Emission reductions on this scale will inevitably involve a switch to low- or zero-carbon energy sources such as renewables
Fossil fuels Temperature increase
Renewable energy prospects to 2020–2030(Case Study)
Renewable energy sources are already providing a significant and increasing proportion of the world’s primary energy, and here we look briefly at the prospects for renewable energy in the European Union (EU) as a whole, and in the United Kingdom (UK) in particular, in coming decades.
EU 2020 targets
The European Union’s ‘20:20:20’ Directive, passed in 2009, set a target for Europe to achieve by 2020 (European Union, 2011):
- a 20% reduction in carbon emissions
- a 20% contribution to gross final energy consumption from renewable sources
- a 20% improvement in the efficiency of energy use.
EU member countries have agreed to produce National Renewable Energy Action Plans showing how they propose to contribute to these 20:20:20 targets. The UK’s 2020 target is to achieve a 15% contribution from renewables.
UK 2020 targets
The UK Government’s Action Plan (DECC, 2010c) concludes that delivering the 15% target is likely to involve renewables supplying approximately:
- 30% of electricity demand, including 2% from small-scale sources
- 12% of heat demand
- 10% of transport demand
- In 2013 the UK Government passed an Energy Act introducing various Electricity Market Reform measures Energy efficiency to take effect after 2015, involving:
- setting ‘strike prices’ for most renewables and other energy sources
- a ‘Contracts for difference’ system to ensures that if the prevailing market price is lower than the strike price the difference will be topped up; equally, if the prevailing market price is higher than the strike price, the generator will have to repay the difference
- establishment of a ‘Capacity Market’ ensuring that sufficient generating capacity is available on standby in case other electricity generation is insufficient to meet demand.
In 2014 the EU decided on new targets, stipulating that by 2030:
- European carbon emissions should be reduced by 40%
- EU energy efficiency should be improved by 30%
- the contribution of renewable energy to EU supplies should reach 27% – but there were no specific renewables targets for individual member countries, such as the UK.
However, the UK Committee on Climate Change in its 2011 report on Renewable Energy (CCC, 2011) envisaged four scenarios for UK renewables by 2030.
As shown in the figure at the start of this section (where H=heat, E=electricity and T=transport), the renewable energy contribution could rise to:
- between 35% and 65% of electricity supplies
- between 35% and 50% of UK heat demand
- between 11% and 25% of transport energy needs.
The figure also suggests that the total contribution of renewables to gross final consumption could be between 28% and 46%, depending on Government policies. These CCC Scenarios, supported by other similar analyses, suggest that the prospects for UK renewable energy in the coming decades look bright.