For decades now scientists have been raising awareness about how the human lifestyle is drastically changing the climate and Earth and that it is vital we change course. Yet the carbon dioxide in the atmosphere continues to increase almost constantly, propelling global warming. According to data from the International Energy Agency, around 36 gigatonnes of carbon dioxide (CO₂) were emitted in 2021 by burning fossil fuels and industrial processes worldwide. 50 years ago it was just 14 gigatonnes.

The global average surface temperature already increased by at least 1.2°C between 1880 and 2020. The global community is now aware of the danger. In 2015, binding targets in accordance with international laws were set at the 21st World Climate Conference in the form of the Paris Agreement. 195 countries pledged to limit the rise of the worldwide average temperature in comparison to the pre-industrial era (1850 to 1900) to significantly under 2°C, if possible to under 1.5°C.

It is possible to roughly estimate how much CO₂ and other greenhouse gases humans can still release into the atmosphere worldwide to maintain this target. This is known as the greenhouse gas budget. Should this be exceeded, then targets will most likely not be achievable. In order to limit the temperature increase to 1.5°C, humanity – calculated from the beginning of 2020 – can only release another 400 gigatonnes (billion tonnes) of CO₂ into the atmosphere; to limit the increase to a maximum of 2°C, some 1,150 gigatonnes. The later we begin to limit emissions, the more drastic the measures will have to be to achieve the temperature target.

At the 26th World Climate Conference in 2021 in Glasgow, Scotland, the groundwork for the implementation of the Paris Agreement was ratified in its entirety, thus beginning the phase in which countries must show that they actually do intend to implement the Agreement. By 2030, for the 1.5°C target, global CO₂ emissions must sink by 45 percent compared to 2010. By 2050, net zero emissions should be achieved. “Net zero” means that humanity does not emit more greenhouse gases than natural sinks such as oceans or forests can absorb or that can be removed from the atmosphere using technology.

The targets are both clearly measurable and verifiable, and more concrete than before. Further, they clearly show how closely protecting the oceans, forests and other ecosystems is linked to climate protection. In addition, countries in the Global South, which have contributed the least to global warming yet will suffer the most from the consequences, have been approved financial support of more than 100 billion US dollars.

The Keeling Curve as a symbol of climate research

Knowledge regarding human-made climate change and the influence of greenhouse gases has developed over the last 200 years. In the 19th century, researchers identified initial links and discovered that Earth’s atmosphere creates a greenhouse effect which keeps the planet at a higher temperature than expected.

Towards the mid-19th century carbon dioxide was identified as the trace gas causing this temperature increase by preventing the infrared radiation from leaving the earth. The number of installed weather stations increased worldwide during this time. It thus became possible to establish a global average, to track the temperature change on Earth and, with the later measurement of CO₂ concentration, to make causal links. In the transition from the 19th to 20th century it became increasingly clear that rising amounts of CO₂ in the atmosphere lead to increasing temperatures and that this can be caused by the burning of fossil fuels.

Yet it was only in 1958 that the continual measurement of CO₂ concentration in the atmosphere began on the volcano Mauna Loa (Hawaii/USA, 3,397 metres above sea level). The first measurement revealed a concentration of 313 ppm (parts per million). In 2021 values over 420 ppm were recorded for the first time. The continual varying rise of CO₂ concentration in the atmosphere over the years has become a symbol of climate research in the form of the so-called Keeling Curve. It graphically represents the average concentration change of CO₂ in the earth’s atmosphere and is named after Charles Keeling from the Scripps Institution of Oceanography in La Jolla, California, USA. The climate researcher, who passed away in 2005, initiated the building of measurement stations (and other stations), recorded data over decades and thus for the first time found convincing proof that humans influence the CO₂ concentration in the earth’s atmosphere by burning fossil fuels.

From Club of Rome to Fridays for Future

Back in 1965 scientists warned a US president about climate change and its consequences for the first time. Charles Keeling was also part of the scientific advisory committee that brought the then president Lyndon B. Johnson’s attention to the significant environmental changes caused by an accumulation of carbon dioxide.

An influential organisation in this area was the Club of Rome, which published the first scientifically based report entitled “The Limits of Growth” in 1972. Although climate change was not one of the main topics, the publication brought the public’s attention to subjects such as resource exploitation, environmental destruction, and overpopulation, and appealed for a sustainable lifestyle in ecological and economic balance.

From the mid-20th century it became ever clearer that the earth’s atmosphere was continually warming due to human activity. In order to counteract this threat, the Environment Programme of the United Nations and the World Meteorological Organization (WMO) founded the IPCC in 1988, the Intergovernmental Panel on Climate Change, also known as the World Climate Council. It is the central scientific body in the global fight against global warming. The committee publishes, among other things, an assessment report every five to six years with a scientific estimate regarding the status quo of the global climate situation.

UN World Climate Conferences, officially called Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change, have been taking place since 1995. Two of the most important outcomes in this context were the Kyoto Protocol in 1997 which came into force in 2005 and the Paris Agreement which was concluded in 2015 and replaced the Kyoto Protocol in 2016.

In 2019 the European Commission suggested the European Green Deal. It resulted in the 2021 European Climate Law, which stipulates that the EU member states will be climate neutral by 2050. By 2030, as part of this transition, net greenhouse gas emissions must be reduced by at least 55 percent in comparison to 1990.

Aside from institutional facilities, independent movements and initiatives have developed over the past years that regularly raise awareness of the climate crisis via demonstrations and campaigns to stir politics and society into action. The Fridays for Future movement is especially well-known. It began when Swedish student Greta Thunberg went on her first school strike for the climate on 20 August 2018 and quickly grew into a global movement.

What is to be done?

Efforts to reduce the concentration of CO₂ and other greenhouse gases can be focused on three approaches. The first and most important approach is the fast and sustainable departure from fossil fuels. This ultimately requires a fundamental transformation of energy conversion worldwide so that industry and society can completely cease burning fossil fuels.

The second approach is based on protecting and expanding natural carbon sinks. Around half of the emissions caused by humans have been absorbed by forests, soils and the oceans. It is uncertain as to how long soils and forests can maintain this, so it is important that we protect these sinks. A third approach consists in the use of technological measures to create so-called negative emissions in which CO₂ is removed from the atmosphere. Many of these processes have however only been tested locally and it is unclear how practical they are on a global scale.

Published: August 2022