In the course of the earth's history, the climate has changed many times. Over many tens of thousands of years, warm periods and ice ages have taken turns. Since the last ice age that came to an end about 11,000 years ago, the global temperature of the earth has steadily risen again. We currently experience a warm (or interglacial) period. Natural climate change is caused by changes in the Earth's radiation budget. The balance (ratio of reflection and absorption) between the sun's incoming energy and the Earth's heat emission determines the radiation budget. Besides the vegetative cover of the earth, the greenhouse effect is the major influence on the radiation balance as, without the greenhouse effect, the average ground temperature of the Earth would be minus 18 degrees Celsius. While the majority of the heat is radiated into space, gases which are present in the earth’s atmosphere, such as water vapour, carbon dioxide or methane, retain a portion of it by absorbing heat into their molecules and then emitting it in all directions. Due to these greenhouse gas emissions, the median temperature at the Earth's surface is plus 15 degrees Celsius.
When, today, the media and politicians speak of climate change, they mean the global warming of the air's temperature, surface and of the seas due to human (anthropogenic) influences. In contrast to natural fluctuations, the rise in the global average temperature triggered by global warming can be felt within a few decades. Since the beginning of systematic measuring of the Earth's temperature in 1880, it has increased by one degree Celsius to date. If the global community does not bring about a decisive reversal in the emission of greenhouse gases, an average rise in global temperatures of 1.8 up to four degrees Celsius is likely to occur by 2100. But even a rise in temperature of 1.8 degrees Celsius would have a massive impact and could lead to more frequent droughts, flooding and hurricanes in many regions of the world.
How do humans change the climate?
Since the industrial revolution in the late 19th century, the greenhouse gases in the atmosphere have increased to such an extent that more and more heat is being retained instead of escaping into space. And so, humans have maximized the natural greenhouse effect. Between 1990 and 2012 alone, global greenhouse gas emissions have increased by 40 per cent. The 1997 Kyoto Protocol from the UN Framework Convention on Climate Change counts carbon dioxide (CO2), methane (CH4) and nitrous oxide (N20), as well as fluorinated greenhouse gases (F-gases), hydrofluorocarbons (HFC), perfluorocarbons (PFC) and sulphur hexafluoride (SF6) among the most damaging greenhouse gases. Since 2015, nitrogen trifluoride (NF3) has been added.
CO2 is produced in large amounts through the use of fossil fuels such as coal, oil and gas and plays the most significant part in the additional greenhouse effect. Ice core drilling verifies the concentrations of CO2 in the air over the course of the last 600,000 years, and that today’s concentration is substantially higher than ever before. The lion's share of global CO2 emissions can be traced back to the generation of electricity and heat, at 40 per cent, while traffic is responsible for 25 per cent.
A strong population growth correlated with the industrial revolution - initially in industrialized countries, later on in the emerging and less developed countries. Between 1960 and 1999, the world's population doubled and has now reached more than seven billion people (2017). In the course of this, people's use of space to settle, for traffic and agriculture at the cost of forests and other natural covers has risen dramatically. These changes have led to increased levels of greenhouse gas emissions as working the soil, among other things, speeds up the release of CO2. Healthy soils bind much more carbon than arable land or settlement areas and in so doing have a much larger influence on the concentration of greenhouse gases.
Methane occurs as a result of organic decaying processes. Besides natural sources, such as moors and permafrost (permanently frozen) soils, factory farming, in particular, is one major cause of methane emissions. Unsustainable agricultural and forest management can also be a source of methane emissions.
Effects on people and the environment
Global warming is expected to bring about melting ice, rising sea levels and an increase in storms and other extreme weather phenomena.
The Arctic is warming particularly quickly, and the air and water temperature there is rising significantly more rapidly than the global average. 40 per cent of the Arctic Sea ice has already melted, and there are fears that the Arctic Sea could already be ice-free by the summer of 2050. Temperatures in Antarctica are also rising more sharply than average, especially in West Antarctica. The Antarctic ice sheet stores about 60 per cent of the total freshwater on earth. If it were to melt entirely, it would lead to a rise in sea levels of over 50 metres. Calculations have shown that between 2002 and 2011 about five times as much ice was lost from the Antarctic landmass per year as was lost in the decade before.
The melting ice at the poles also contributes to a change in sea currents, for example, the Gulf Stream or the Humboldt Current.
But it is not just there; ice is also melting in the mountain ranges of the world: Between 1993 and 2009, the global ice mass receded by 275 billion tonnes. Even if not every receding glacier is caused by climate change, researchers also see a significant link between this and global warming. Global warming could also cause the permafrost soils of the northern continents (in particular northern Canada, Alaska, Greenland, East Siberia) to thaw. This would release large quantities of the carbon and methane stored there and exacerbate the greenhouse effect.
According to current estimates, the sea level is rising by three millimetres per year. This is approximately twice as much as at the beginning of the 20th century. In addition to meltwater from glaciers and the poles, the warming of the oceans and the resulting expansion are responsible for this. Even if limiting the rise in temperature globally to two degrees Celsius above the pre-industrialization level were successful, the research organization Climate Central estimates that 130 million people in coastal regions will suffer because of the 4.5-metre sea level rise that this would cause. A sea level rise at four degrees would be 7.4 metres and would endanger between 470 and 760 million people worldwide. These developments would show the most in China. But even in Germany, 1.3 million people would feel the impact of the rising levels.
Global warming also leads to more pronounced fluctuations in temperature and precipitation and the weather extremes connected with those. Thus, on the one hand, rainfall and torrential rain have increased; however, on the other hand so have desiccation and droughts. Heatwaves have also become more common: Since the onset of the industrial revolution, there has been a fourfold increase; at a rise in temperature of four degrees Celsius the increase would be 62-fold.
Extreme weather conditions lead to crop failures. This is expected particularly in the regions of the world that are already affected by famine anyway. Negative effects are also expected with respect to the development of global poverty. The World Bank estimates that by the year 2030, 100 million people will join those already living in extreme poverty due to the impact of global warming.
Political reactions to climate change
The Intergovernmental Panel on Climate Change – IPCC was founded as early as in 1988. This panel is a scientific body that evaluates the current status of research and presents it in reports of its own. The IPCC reports serve as a basis for international climate policy, which was institutionalized with the first UN Conference on Environment and Development (also called The Earth Summit) in Rio de Janeiro in 1992. There, the Framework Convention on Climate Change was signed which meanwhile has been ratified by all UN member states. All members are committed to report regularly on their greenhouse gas emissions and meet on an annual basis to discuss concrete measures on climate protection.
A further milestone was the agreement of the Kyoto Protocol at the third Climate Change Conference in 1997. For the first time ever, industrialized countries promised to reduce their greenhouse gas emissions. An extension of the Protocol to 2020, however, failed as the number of ratifying countries was too small. Moreover, Russia, Canada, Japan and New Zealand declared their withdrawal from the Protocol.
During the COP21 (21st climate conference), the Paris Agreement, a follow-up agreement for the Kyoto Protocol was adopted that came into force just under one year later. In detail, it was agreed to keep the global rise in temperature well below two degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius. Global greenhouse gas emissions must be reduced drastically to less than half the 1990 level by 2050 to achieve this. To make this process fair, according to the German Federal Environmental Protection Agency, the lion’s share of this must be taken on by industrialized nations, and they would have to reduce their greenhouse gas emissions by 80 per cent by 2050 (compared to 1990).
In contrast to the Kyoto Protocol, the Paris Agreement was initially also ratified by the United States. The by far largest economy in the world is, after China, the second-largest emitter of greenhouse gasses and therefore plays a key role in climate politics. Under the new political leadership, however, the United States changed its course and declared in summer 2017 its withdrawal from the Agreement. This decision to withdraw is controversial in the US political landscape —several federal states have joined forces and have announced that they will continue to adhere to the Agreement. Growing concerns that other countries would imitate the withdrawal of the United States and thus endanger the entire Agreement were unfounded when states parties jointly negotiated with each other on concrete instruments for the implementation of the Agreement at the COP23 in Bonn. At the summit, 20 countries joined an anti-coal alliance and declared that they would abandon the production of electricity from coal-fired power stations by 2030. It is planned that the final decisions on the concrete implementation of the Paris climate agreement will be taken in 2018 in Katowice (Poland).
Criticism of the climate talks
Since the beginning of the climate talks in the early 1990s, global CO2 emissions have continued to increase by more than 50 per cent. There is a marked discrepancy between objectives put down on paper and objectives that have actually been achieved. There is also a major imbalance in the contribution of burdens and costs. While the consequences of climate change are on a global scale, those most responsible for it are industrialized and emerging countries that continue to use fossil fuels. Small island states in the Pacific Ocean are already suffering hugely from the effects of climate change—entire groups of islands will be uninhabitable in the future. From the point of view of the affected island states, the agreements do not go far enough; they demand much more stringent rules for the scaling-down of the greenhouse gas emissions as well as for fair rules for the distribution of incurring costs.
Besides the question of climate justice, various environmental groups and academics query the basic assumption of the UN negotiations that continued economic growth with less natural resource consumption will lead to a solution of the problems. They criticize that the focus is on purely technological solutions and economic mechanisms and that alternative concepts and ideas that may be critical of economic growth are not taken into consideration.
The challenges brought about by climate change are therefore twofold: Its extent must be limited by climate protection, and the already unavoidable effects overcome by adaptation. The necessary measures for this are, however, expensive: The World Bank has calculated that even containing global warming to two degrees Celsius per year, 70 to 100 billion euro will still be required to fight the impacts that have already occurred.
Sources and further information:
- Intergovernmental Panel on Climate Change (IPCC); IPPC Reports
- Dossier über den Klimawandel – Bundeszentrale für politische Bildung
- Juergen Päger. Ökosystem Erde (German)
- Germanwatch e.V. - Climate risk index
- German Council of Environmental Advisors (WBGU), Special Report
- German Federal Environmental Protection Agency - Climate Change
- Bauriedl, Sybille (Hrsg.) 2015: Wörterbuch Klimadebatte. Bielefeld: Transcript-Verlag. (German)