What is climate change in the political context

Environmental policy

Felix Christian Matthes

To person

Dr., is the coordinator of the energy and climate protection division at the Öko-Institut Berlin. Research focus: national and international energy and climate protection policy.

Contact: [email protected]

Temperatures on earth are rising - not least as a result of human activities. In order to limit the effects of climate change, greenhouse gas emissions must be reduced worldwide.

In order to limit the consequences of climate change, greenhouse gases are to be reduced. (& copy picture-alliance / AP)


The climate change caused by human activities paradoxically amplifies an effect that made life on earth possible in the first place. The so-called greenhouse gases in the earth's atmosphere reduce the heat reflection from the earth's surface into space and store the corresponding energy in the earth's atmosphere. Without the natural greenhouse effect, which is mainly caused by the water vapor (especially clouds) and carbon dioxide (from organic cycles) in the atmosphere, the average temperature of the earth near the ground would not be around 14 ° C above, but around 19 ° C under zero.

Anthropogenic greenhouse effect

In addition to this vital natural greenhouse effect, the human-made (anthropogenic) greenhouse effect has occurred since the beginning of industrialization in the 19th century. It is due to the rapid increase in emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and other synthetic gases that are concentrated in the atmosphere. The concentration of CO2 in the earth's atmosphere has risen from 280 ppmv (parts per million in volume, millionths of a volume) to currently 377 since the pre-industrial era, while the methane concentration has risen from 730 ppbv (parts per billion in volume, billionths of a volume) 1847 ppbv, with nitrous oxide from 270 to 319 ppbv. Other greenhouse gases such as chlorofluorocarbons (CFC), hydrogen-containing fluorocarbons (HFC) or perfluorinated hydrocarbons (PFC) and sulfur hexfluoride (SF6) do not occur in the natural composition of the earth's atmosphere. They have increased significantly in their concentrations over the past few years.

The greenhouse effect
The current concentrations of the various CFCs are up to 545 pptv (parts per trillion in volume), 14 pptv for various HFCs and around five pptv for SF6. The synthetic greenhouse gases CFC, HFC, PFC and SF6 are particularly explosive because they sometimes remain in the atmosphere for an extraordinarily long time (for example, for SF6 for 3200 years) and have a consistently high greenhouse effect.

In the meantime, it has largely been proven beyond any doubt that this increase in greenhouse gas concentrations contributed significantly to the increase in the global average temperature near the ground of around 0.74 ° C (± 0.2 ° C) observed in the last century. Now there have always been natural fluctuations in the average temperatures within very long periods (warm and cold periods). However, it is not only the magnitude of the temperature rise that is worrying, but above all its speed. Never in the last 1000 years has such a rapid rise in temperature been recorded. At the same time, the concentration of the most important greenhouse gas CO2 has never increased so quickly in the last 20,000 years. Today it records values ​​that have not been achieved in the past hundred thousand years.

Projections for the future development of greenhouse gas emissions and model calculations for the resulting climate effects show that the global average temperature near the ground could increase by between 1.1 and 6.4 ° C towards the end of the 21st century compared to 1990. The range of temperature forecasts is not only due to scientific uncertainties, but also takes into account different emission trends. Depending on the assumed emission profiles, the best estimate is a range of temperature increases of 1.8 to 4.0 ° C. If the emission trends observed today continue, a temperature increase of 3.4 to 4.0 ° C (with an uncertainty of the models of around ± 1 ° C) can be expected for the year 2100 - also compared to 1990. The consequences of such a large and rapid increase in temperature can be serious.

Consequences for ecosystems and societies

Global warming can lead to various effects, which in turn can have a significant impact on ecosystems and human societies. It must be taken into account that the temperature increases caused by the greenhouse effect do not occur evenly. Temperatures will rise more markedly over the land masses of the continents than over the oceans. It is now very likely that the following changes will occur:
  • The sea level rises significantly (due to the thermal expansion of the water masses and the melting of the polar caps),
  • Glaciers are melting
  • the extreme temperatures increase,
  • Temperature spreads in the course of the day decrease,
  • Precipitation will be heavier and
  • Dry times are getting longer, which increases the risk of drought.

Source text

Climate research on the dying glacier

[...] In the Schneefernerhaus, 2,650 meters above sea level, the natural scientist Ludwig Ries only has an unadorned office, but a grandiose view: the alpine panorama, with a view of Italy when the weather is good. [...] The official keeps a record of the consequences of the industrial lifestyle.

Nowhere in Germany does it work better than on the Zugspitze, far away from cars and factories. Up here, unadulterated by local exhaust gas sources, one can observe how the earth's atmosphere is changing. This is exactly what Ludwig Ries registers, supported by an armada of mechanical helpers.
Ries notices, for example, how the earth breathes. In summer, when the trees north of the equator bear leaves and convert carbon into oxygen through photosynthesis, it regularly measures lower carbon dioxide values ​​than in winter, when many plants are dormant. However, Ries also observes a different, frightening regularity: year after year, summer and winter, he discovers more carbon dioxide in the Zugspitze air - more of that non-toxic gas that escapes from exhaust pipes, chimneys, chimneys, accumulates in the atmosphere and is decisive for global warming cares. At least that's what most climate researchers are convinced of. Ries too. Every five minutes, his sensitive laboratory, a custom-made product, evaluates a little bit of Zugspitz air. From this, Ries calculates half-hourly values, daily values, monthly values, and finally an annual value, determined from more than 100,000 individual measurements. Ries is interested in tiny numbers; he is interested in the third or fourth digit after the decimal point, the millionths of a fraction of carbon dioxide in the air. The unmistakable tendency: there are more and more millionths. In October 1999, shortly after Ries began measuring, he tracked down 365; in October 2004 the value had climbed to 376 (value of this special measuring point - editor's note).
11 millionths more - that may seem like little to laypeople, but not to experts like Ries. Air bubbles in the eternal ice have revealed to researchers how many millionths of CO2 were in the air before people started burning coal, oil and gas on a large scale: 280. Since then, the remains of factories, houses and cars have had the CO2 concentration increase by around 100 millionths, 10 percent of it during the past five years alone. [...]
When Ludwig Ries looks out of his study, his gaze falls on the remnant of the supposedly eternal ice: the dying Schneeerner. The glacier once covered 300 hectares, but has now shrunk to less than 50. In 25 years at the latest, he will be gone, lightened up by the summer sun: a victim of climate change.
Earlier, between 1961 and 1990, during the last so-called normal climatological period, observers from the German Weather Service measured average summer temperatures of 1.5 degrees on the Zugspitze summit. The Schneeerner shrank, but the winter snowfalls caused ice to grow back. It still snows on the Zugspitze today, but the ice losses in summer are no longer made up for by new snow in winter: the thermometer showed 2.2 degrees in the summer of 1999, then 2.3, then 2.4, and finally 3 in the following years , 2, last year even 5.2 degrees. That alone cost several meters of ice [...].
Worldwide, the average temperature has risen by 0.7 degrees in the past century, in Germany by 0.9 degrees. [...] Climatologists know that even small changes in meteorological mean values ​​make extreme weather events many times more likely. According to the German Meteorological Service, Germany is, for example, hit by so-called trough locations much more frequently than before, a weather situation that brought heavy rainfall and devastating floods to the Elbe catchment two years ago. Meanwhile, the Frankfurt meteorologist Christian-Dietrich Schönwiese has calculated that the probability of a hot summer like 2003 has risen twenty-fold over the past two decades.
"We are feeling the effects of global climate change more and more," says the latest natural catastrophe report from Munich Reinsurance. The company commented on the heat of the past year with the words: "The future has already begun." [...]

Fritz Vorholz, "Germany in Fever", in: Die Zeit No. 51 of December 9, 2004



The increase in other extreme weather events such as hurricanes or typhoons caused by climate change has not yet been conclusively proven; however, the probability of such effects is by no means negligible. In the long term, serious disruptions to global cycles can also arise, such as the irreversible demolition of the Gulf Stream in the Atlantic, the transport of which ensures the comparatively warm climate of Europe.

Such changes have consequences. For example, in regions where the water balance is already under heavy strain, the problems of water supply will increase. Regions whose water supply is largely fed by glaciers will also face new challenges. The increased intensity of precipitation on the one hand and the risk of higher extreme temperatures and droughts on the other hand can lead to problems for the food supply in many regions. Both the rise in sea level and the intensity of precipitation are very likely to increase the risk of flooding for some regions of the world, with the often densely populated coastal regions being particularly - but by no means only - affected. The shift in climate and vegetation zones and the tendency towards more extreme temperatures will increase health problems - such as an increased risk from malaria, dengue fever or heat stress. The relationship between increased extreme temperatures and the number of deaths from heat stress, for example, has now been well proven statistically.

With the shift of temperature and vegetation zones as well as the severity of various weather events, many ecosystems on earth (from arctic habitats to Australian underwater reefs) are foreseeably irreversibly damaged by global climate change.

Cartoon: global warming
A key feature of climate change is that its consequences are unevenly distributed across the earth. The capacities of the various societies to mitigate or offset at least some of the effects of climate change (from the construction of dykes and dams to health care) vary widely. The vulnerability of many developing countries to the consequences of climate change is significantly higher than that of the highly developed industrialized countries. They suffer from less favorable climatic conditions, a lack of capital, poor infrastructure and deficits in education. Not only the scientific phenomenon of climate change, but also its political dimension is global in nature. The industrialized countries are responsible for most of the greenhouse gas emissions today, with consequences above all for the developing countries. An important dimension of climate change is therefore also the global distributive effect of its consequences. Against this background, the climate problem also gives rise to considerable security policy problems and the need for action.

The various mechanisms of global climate change and its consequences for nature and people are far from being conclusively researched. However, the scientifically proven findings that are already available make it possible and necessary to set targets with which the consequences of climate change can be limited to a level that can be barely tolerated or compensated for.

The "2 degree approach", according to which the increase in the global mean temperature by the end of this century is to be limited to a maximum of two degrees compared to the temperature level in the pre-industrial era, is of increasing importance here. As an additional condition, some analyzes demand, in addition to this long-term limit, the rate of temperature rise to a maximum of 0.2 ° C per decade.

Transferred to the associated limitation of global greenhouse gas emissions, this means reducing their occurrence by at least 50 percent by the middle of the century, depending on the timing of the emission curve (when will the global peak of emissions be reached and how quickly will they then be reduced) to be avoided almost entirely by the end of the century.