Climate change and air
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Image © Ace & Ace/EEA
Global warming induces long periods of drought. Drought favours increasing numbers of forest fires.
Ivan Beshev, Bulgaria (ImaginAIR)
In 2009, a joint British and German team of researchers conducted research off the coast of Norway with a type of sonar normally used to search for shoals of fish. The team was not there to look for fish but to observe one of the most powerful greenhouse gases, methane, being released from the ‘melting’ seabed. Their findings were only one among many in the long timeline of warnings about the potential impacts of climate change.
In regions close to the poles, a part of the land mass or the seabed is permanently frozen. According to some estimates, this layer — known as permafrost — contains twice the amount of carbon that is currently in the atmosphere. Under warmer conditions, this carbon can be released from rotting biomass as either carbon dioxide or methane.
‘Methane is a greenhouse gas more than 20 times more powerful than carbon dioxide,’ warns Professor Peter Wadhams of Cambridge University. ‘So now we risk facing further global warming and even faster melting in the Arctic’.
Methane emissions come from human activities (mainly agriculture, energy and waste management) and natural sources. Once released into the atmosphere, methane has a lifespan of around 12 years. Although it is considered to be a relatively short-lived gas, its lifespan is still long enough for it to be transported to other regions. In addition to being a greenhouse gas, methane is also a contributor to the formation of groundlevel ozone, which itself is a major pollutant affecting human health and the environment in Europe.
Particulate matter can have a warming or cooling effect
Carbon dioxide may be the largest driver of global warming and climate change but it is not the only one. Many other gaseous or particulate compounds, known as ‘climate forcers’, have an influence on the amount of solar energy (including heat) the Earth retains and the amount it reflects back into space. These climate forcers include main air pollutants such as ozone, methane, particulate matter and nitrous oxide.
Particulate matter is a complex pollutant. Depending upon its composition, it may have a cooling or warming effect on the local and the global climate. For example, black carbon, one of the constituents of fine PM and a result of incomplete burning of fuels, absorbs solar and infrared radiation in the atmosphere and thus has a warming effect.
Other types of PM containing sulphur or nitrogen compounds have the opposite effect. They tend to act as small mirrors, reflecting the sun’s energy and thus leading to cooling. In simple terms, it depends on the colour of the particle. ‘White’ particles tend to reflect sunlight, while ‘black’ and ‘brown’ particles to absorb it.
A similar phenomenon occurs on land. Some of the particles deposit with rain and snow or simply land on the Earth’s surface. But black carbon can travel quite far from its place of origin and land on the snow and ice cover. In recent years, black carbon depositions in the Arctic have increasingly darkened the white surfaces and reduced their reflectivity, which means that our planet retains more heat. With this additional heat, the size of white surfaces is shrinking ever more quickly in the Arctic.
Interestingly, many climate processes are controlled not by major constituents of our atmosphere but by some gases that are only found in very small amounts. The most common of these so-called trace gases, carbon dioxide, constitutes only 0.0391 % of the air. Any variation in these very small amounts has the power to affect and alter our climate.
More or less rain?
Their ‘colour’ is not the only way that particles suspended in the air or deposited on the ground can affect the climate. Part of our air consists of water vapour — tiny molecules of water suspended in the air. In their more condensed form, we all know them as clouds. And particles play an important role in how clouds come about; how long they last; how much solar radiation they can reflect; what kind of precipitation they generate and where; and so on. Clouds are obviously essential for our climate; the concentrations and composition of particulate matter might actually change the timing and location of traditional rainfall patterns.
Changes in precipitation amounts and patterns have real economic and social costs, as they tend to affect global food production and consequently food prices.
The EEA’s report ‘Climate change, impacts and vulnerability in Europe 2012’ shows that all regions in Europe are affected by climate change, causing a wide range of impacts on society, ecosystems and human health. According to the report, higher average temperatures have been observed across Europe, combined with decreasing precipitation in southern regions and increasing precipitation in northern Europe. Furthermore, ice sheets and glaciers are melting and sea levels are rising. All of these trends are expected to continue.
(c) Dovile Zubyte, ImaginAIR/EEA
The relationship between climate change and air quality
Although we do not have a complete understanding of how climate change might affect air quality and vice versa, recent research indicates that this mutual relationship might be stronger than estimated previously. In its assessments from 2007, the Intergovernmental Panel on Climate Change — the international body set up to assess climate change — predicts a decline in air quality in cities in the future due to climate change.
In many regions across the world, climate change is expected to affect local weather, including the frequency of heat waves and stagnant air episodes. More sunlight and warmer temperatures might not only prolong the periods of time in which ozone levels are elevated, it may also exacerbate peak ozone concentrations further. This is certainly not good news for southern Europe, which is already struggling with episodes of excessive ground-level ozone.
International discussions on mitigating climate change have agreed to limit the global mean temperature increase to 2° Celsius above pre-industrial era levels. It is not yet certain if the world will succeed in curbing greenhouse gas emissions sufficiently to attain the 2-degree target. Based on several different emissions trajectories, the United Nations Environment Programme identified the gaps between the current pledges to cut emissions and the cuts we need to attain the target. It is clear that more efforts are needed to reduce emissions further in order to increase our chances of limiting the temperature increase to 2 degrees.
Some regions — like the Arctic — are projected to warm much more. Warmer temperatures above both land and oceans are expected to affect humidity levels in the atmosphere, and this could in turn affect precipitation patterns. It is not yet fully clear the extent to which higher or lower concentrations of water vapour in the atmosphere might affect precipitation patterns or the global and local climate.
However, the extent of the climate change impacts will partly depend on how different regions adapt to climate change. Adaptation actions — from improved urban planning to adaption of infrastructure such as buildings and transport — are already taking place across Europe, but more such actions will be needed in future. A wide spectrum of measures can be used to adapt to climate change. For example, planting trees and increasing green spaces (parks) in urban areas alleviates the effects of heat waves, while also improving air quality.
(c) Bojan Bonifacic, ImaginAIR/EEA
Win-win scenarios possible
Many climate-forcers are common air pollutants. Measures to cut emissions of black carbon, ozone or ozone precursors benefit both human health and the climate. Greenhouse gases and air pollutants share the same emission sources. Therefore there are potential benefits that can be obtained by limiting emissions of one or the other.
The European Union aims to have a more competitive economy with lower dependence on fossil fuels and less impact on the environment by 2050. In concrete terms, the European Commission aims at reducing the EU’s domestic greenhouse gas emissions by 80–95 % compared to their 1990 levels by that date.
The transition to a low-carbon economy, and substantial reductions to greenhouse gas emissions, cannot be achieved without reshaping the Union’s energy consumption. These policy objectives target a reduction in final energy demand; a more efficient use of energy; more renewable energy (e.g. solar, wind, geothermal and hydro); and less use of fossil fuels. They also foresee a wider application of new technologies, such as carbon capture and storage, where carbon dioxide emissions from an industrial facility are captured and stored underground, mostly in geological formations from where it cannot escape into the atmosphere.
Some of these technologies — carbon capture and storage in particular — may not always be the best solution in the long-term. However, by preventing large amounts of carbon from being released into the atmosphere in the short- and the medium term, they may help us mitigate climate change until the moment that long-term structural changes start being effective.
Many studies confirm that effective climate and air policies can benefit each other. Policies aimed at reducing air pollutants might help keep the global mean temperature increase below two degrees. And climate policies aimed at reducing black carbon and methane emissions might reduce the damage to our health and the environment.
But it is not the case that all climate and air quality policies are necessarily mutually beneficial. The technology used plays an important role. For example, some of the carbon capture storage technologies used might help improve Europe’s air quality, but others might not. Equally, the replacement of fossil fuels with biofuels might reduce greenhouse gas emissions and help meet climate targets. But at the same time, it could increase the emissions of particulate matter and other carcinogenic air pollutants, hence deteriorating Europe’s air quality.
A challenge for Europe is to ensure that air and climate policies for the next decade promote and invest in ‘win-win’ scenarios and technologies that are mutually reinforcing.
(c) Ivan Beshev, ImaginAIR/EEA
- EEA core set of indicators: CSI 013 on Atmospheric greenhouse gas concentrations
- EEA Report No 12/2012 - Climate change, impacts and vulnerability in Europe 2012
- Climate-ADAPT: Web portal on climate change adaptation information
- The EU Climate and Energy Package
- UNEP - Integrated Assessment of Black Carbon and Tropospheric Ozone
For references, please go to http://www.eea.europa.eu/signals/signals-2013/articles/climate-change-and-air or scan the QR code.
PDF generated on 03 Dec 2016, 09:00 AM