Conclusion
In this course:
- Section 1 has described the basic principles of the greenhouse effect, the action of greenhouse gases and how the temperature of the Earth’s surface has been maintained at the ‘right temperature’ for life to develop.
- Section 2 has described the principles of the global carbon cycle, and how this has been disturbed by human influences, particularly the large scale burning of fossil fuels. This has led to a rising concentration of carbon dioxide in the atmosphere resulting in additional warming of the whole planet and climate change.
- Section 3 has described two major causes for concern: the rapid rise in global mean surface temperature, particularly since the 1970s, and the increase in extreme weather events.
- Section 4 described the international climate talks that have been taking place since the 1990s, and their role in shaping national policies to keep the global temperature rise to ‘well below 2°C’ by 2100.
- Section 5 described scenarios for the large and rapid reductions in emissions of greenhouse gases that will be needed in the next few decades. It also described how there will need to be a major ‘transition away from fossil fuels’ towards renewable energy, particularly solar and wind power.
- Section 6 described a range of technological (and other) options that will need to be deployed to cut greenhouse gas emissions. These include the wide-spread deployment of energy efficiency and the replacement of fossil fuelled heating and road transport with heat pumps and battery electric vehicles. There will need to be an enormous expansion of renewable electricity generation, particularly from solar and wind power.
This video summarises the material in this course. It can be viewed at one time or as two sections. The first part recaps Sections 1 to 3 of this course. The second part recaps Sections 5 and 6.
Download this video clip.Video player: Video 3: From COP promises to a net-zero pathway.
Transcript: Video 3: From COP promises to a net-zero pathway.
INSTRUCTOR
Climate change, from COP promises to a net zero pathway. Carbon dioxide is the most important of a range of greenhouse gases. Its presence in the atmosphere has been contributing to the greenhouse effect. This is warming which occurs when the atmosphere traps heat radiated from the Earth toward space. The carbon dioxide in the atmosphere is part of a global carbon cycle. It is emitted into the atmosphere by a range of processes and also continuously reabsorbed, both on land and in the sea. In pre-industrial times, this cycle was in balance, and the atmospheric carbon dioxide concentration was stable. However, human activities have moved it out of balance, resulting in a rising carbon dioxide atmospheric concentration. The main source of carbon dioxide emitted into the atmosphere as a result of human activities is the combustion of fossil fuels. It is also produced by deforestation, where timber is burned and not regrown.
The production of cement for construction also emits a significant amount of carbon dioxide. Methane is another important greenhouse gas. It is produced by rotting vegetation, such as in landfill sites and rice paddy fields. Cattle and other animal livestock release methane as part of their digestive processes. Natural gas is mainly methane, and it can leak into the atmosphere during fossil fuel extraction and distribution. Methane is slowly oxidised in the atmosphere to carbon dioxide and thus is part of the overall carbon cycle. Nitrous oxide is another powerful greenhouse gas that is produced by decomposing agricultural fertilisers. There are small amounts of other greenhouse gases, which are used in refrigeration, air conditioning and industrial processes. The plot of carbon dioxide concentration against time is called the Keeling Curve. Its concentration was about 280 parts per million in pre-industrial times and reached 317 parts per million in 1960. It reached 420 parts per million in 2023, 50% above pre-industrial levels. This increase in carbon dioxide concentration is causing global warming and climate change. Between 1950 and 2010, global carbon dioxide emissions from fossil fuel burning increased at a rate of about 500 million tonnes per year. However, the rate of increase has slowed since 2010, and the world may now be at its peak rate of carbon dioxide emissions.
If carbon dioxide and other greenhouse gas emissions continued at their 2022 rate to the end of the century, what would happen to the concentration of carbon dioxide in the atmosphere and the global mean surface temperature?We will be continuing to put more carbon dioxide into the atmosphere than is reabsorbed from the atmosphere by land and sea. The atmospheric carbon dioxide concentration will continue to increase at the same rate. By the year 2100, it would have increased by 50% from its 2022 value, reaching about 630 parts per million. The global mean surface temperature rise is likely to have reached about 3 degrees Celsius and would still be rising. This poses the threat of dangerous climate change and has prompted international action to reduce carbon dioxide emissions.
The situation is very urgent. The average global surface temperature between 2011 and 2020 was 1.1 degrees higher than the average over the last half of the nineteenth century. The temperature has been increasing rapidly since the 1970s and continues to increase. The recent global temperature rise has not been evenly distributed. It has been concentrated in the northern hemisphere, and particularly the Arctic. The participants at the 2015 COP 21 meeting in Paris agreed that the global temperature rise by the end of the century should be kept to well below 2 degrees Celsius and that there should be efforts to limit it even further, to 1.5 degrees Celsius.
This target was reaffirmed at the later COP meetings. But what changes in carbon dioxide emissions do these targets require?The Intergovernmental Panel on Climate Change, IPCC, has produced projections of future global greenhouse gas emissions. They estimated that national policies put in place by 2020 might keep emissions very roughly constant, as shown by the dashes on the chart, rather than following the past increasing trend. However, limiting global temperature rise will require future drastic emission reductions.
To limit global temperature rise to 2 degrees, overall greenhouse gas emissions will need to fall rapidly. Carbon dioxide emissions will need to be halved by 2040 and fall to net zero by 2070. In order to keep the temperature rise down to only 1.5 degrees, the reduction in emissions will have to take place even faster.
It has been recognised that a large proportion of methane emissions are associated with food production, so reducing them will be difficult. To date, the main climate change policies have concentrated on reducing carbon dioxide emissions. In order to meet a 1.5-degree target, carbon dioxide emissions will need to fall to net zero by around 2050. The IPCC projection shows that limiting the temperature rise to 2 degrees Celsius by 2100 will require cutting global carbon dioxide emissions by a factor of 6 by 2055, and right down to net zero by 2070.If we achieve net zero by 2070, emissions and absorption will then become in balance. The atmospheric carbon dioxide concentration should stabilise at about 470 parts per million, with the global temperature reaching 2 degrees above its pre-industrial level by 2100.The term ‘net zero’ does not mean that there will not be any greenhouse gas emissions due to human activities at all. Rather, it is a state where the global warming effects of the remaining low positive level of emissions are balanced by carbon dioxide removals from the atmosphere. These can be achieved by deliberate policies, such as the reforestation of large areas of land.
Keeping the temperature rise to well below 2 degrees Celsius and restricting it to only 1.5 degrees will require even faster cuts in carbon dioxide emissions. They will need to be reduced by a factor of 6 by 2040 and become net zero by 2050. The atmospheric carbon dioxide concentration might reach a peak of about 435 parts per million by 2035 and then fall slowly to about 405 parts per million by 2100.The temperature rise of 1.5 degrees Celsius is likely to be long-lasting, and the consequent environmental effects are likely to be experienced well into the 22nd century. These large emissions cuts will need drastic changes to significant elements of our economies and everyday lives. How can governments create practical policies to implement them?The International Energy Agency is an intergovernmental organisation which regularly produces detailed economic analysis of world energy use. In 2023, they produced a scenario for the changes that would be needed to reduce global carbon dioxide emissions from energy to net zero by 2050. Their statistics showed that in 2022, fossil fuels, coal, oil, and natural gas made up just over three quarters of world energy consumption.
Reducing carbon dioxide emissions by a factor of 6 will require a dramatic reduction in fossil fuel use, and particularly that of coal. In the International Energy Agency’s scenario, by 2040, fossil fuels only make up 30% of world energy supply. There will need to be an enormous expansion of renewable energy, particularly solar and wind power, to meet the world energy demand.A whole range of energy technologies will need to be deployed. The best practise in energy efficiency will need to be used to keep total world energy demand down. This will include energy efficiency retrofits of a large proportion of the existing building stock. There will need to be widespread electrification of present-day energy services. A large proportion of the world’s fossil-fuelled heating systems will need to be replaced by electric heat pumps. The bulk of the world’s fleet of fossil-fuelled road vehicles will need to be replaced with battery electric or hydrogen-powered vehicles.
World electricity generation has been steadily increasing right through the 20th century. An increasing proportion of the world’s population now has access to electricity. This graph shows that by 2040, the annual amount of electricity generated will need to be double its 2022 value to replace energy services currently supplied by fossil fuels. Also, almost all fossil-fuelled electricity generation will need to have been phased out and replaced with that from other technologies. By 2040, globally, the annual amount of solar-generated electricity will need to have increased from its 2022 value by a factor of almost 20. Worldwide, these solar systems could cover an area of about 70,000 square kilometres, equivalent to about a third of the area of the UK.
Also by 2040, the amount of global electricity generated from wind power, offshore and onshore, will need to have been increased from its 2022 value by a factor of 8. If this was all done using offshore wind turbines, they would require an area roughly equal to 3 times that of the North Sea. Hydrogen produced from surplus solar and wind power will need to be developed as a fuel and used for energy storage. This transition away from fossil fuels may sound very expensive. But the mass production of solar panels in China and wind farm development in Europe have made large-scale solar PV electricity and electricity from onshore wind cheaper than that from fossil-fuelled electricity. That from offshore wind turbines is now competitive with that from fossil fuels. There has to be a large shift in financial investment away from fossil fuels and into energy efficiency and renewable energy.
There are, of course, many issues of lifestyle that will need to be taken into account. For example, in transport, cutting CO2 emissions will require a move away from individual car use to less energy-intensive modes, such as walking, cycling and public transport. New low-carbon aircraft fuels will need to be developed. Until this is done, there will need to be less flying. There will need to be lifestyle changes in diet, with a move away from meat, particularly beef and lamb, as well as dairy products, to a more vegetarian diet. Global CO2 and methane emissions need to be cut drastically, starting immediately. There needs to be a rapid transition away from the use of fossil fuels. This requires both a deployment of technological solutions and lifestyle changes.
The real problem is that of delay. A six-fold reduction in carbon dioxide emissions is needed by 2040 to limit the global temperature rise to 1.5 degrees Celsius by 2100. However, if that reduction target were to be met only 15 years later, in 2055, then the result is likely to be a 2-degree temperature rise. Every step to reduce global warming will decrease the environmental risks. Every increment of global warming will worsen the environmental problems. These include increased frequency and intensity of heatwaves with associated wildfires, increased damage from floods and storms, and loss of land due to rising sea levels. Immediate action is essential. The good news is that there are many options available to make drastic cuts in greenhouse gas emissions. These include the adoption of new technologies and lifestyle changes. The natural take-up of carbon dioxide from the atmosphere can be improved by stopping deforestation and planting more trees.
Video 3: From COP promises to a net-zero pathway.
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This free course is an adapted extract from the Open University course U116 Environment: journeys through a changing world [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .