Climate change is a long-term change in the Earth's climate and weather patterns. It took almost a century of research and data collection to convince the vast majority of the scientific community that human activity can change the climate of our entire planet. Experiments in the 19th century that suggested that carbon dioxide (CO₂) and other man - made gases may accumulate in the atmosphere and thus isolate the Earth, met with curiosity rather than any concern. In the late XNUMXs, it brought measurements of CO levels₂ the first data to confirm the theory of global warming. Sufficient data, together with climate models, ultimately pointed not only to the reality of global warming, but also to a number of its dire consequences.

Early signs that people can change the global climate

Already in the days of ancient Greece, there were numerous claims that mankind was able to change the air temperature and influence the amount of precipitation through the felling of trees, plowing of fields or irrigation of deserts. One of the theories of climatic effects, which was widely popular until the time of the so-called. Dust bowls (Dust bowl) in the 30s, claimed that "rain follows the plow". It was based on the now refuted idea that tillage and other agricultural practices lead to increased rainfall.

Whether they were real or not, these perceived climatic effects were only local. The idea that people could somehow change the climate on a global scale seemed a bit hair-raising for centuries.

Greenhouse effect

In the 20s, the French mathematician and physicist Joseph Fourier stated that the energy entering our planet in the form of sunlight must be balanced by the energy returning to space because the heated surface produces back radiation. However, he concluded that some of this energy was apparently retained in the atmosphere and did not return to space, which kept the Earth warm. He suggested that the thin layer of air around the Earth - its atmosphere - works similarly to a greenhouse.

Energy enters through the glass walls, but then remains trapped inside, much like in a heated greenhouse. Experts later pointed out that the analogy with the greenhouse was too simplified, because the outgoing infrared radiation is not captured by the Earth's atmosphere, but rather absorbed. The more greenhouse gases there are, the more energy is retained in the Earth's atmosphere.

Greenhouse gases

The theory of the greenhouse effect analogy persisted, and about 40 years later, Irish scientist John Tyndall began to study in detail which types of gas were most likely to play a role in absorbing solar radiation. Tyndall's laboratory tests in the 60s showed that coal gases (containing CO₂, methane and volatile hydrocarbons). Finally, he proved that CO₂ acts as a sponge that can absorb sunlight of different wavelengths.

In 1895, Swedish chemist Svante Arrhenius became interested in how declining CO₂ in the Earth's atmosphere to cool. In an effort to explain past ice ages, he considered whether a decline in volcanic activity could reduce global CO levels₂. His calculations showed that if the level of CO₂ halved, global temperatures could drop by about 5 degrees Celsius (9 degrees Fahrenheit). Next, Arrhenius wondered if the other way around.

He returned to his calculations and this time examined what would happen if the CO level₂ doubled. This possibility seemed distant at the time, but its results suggested that global temperatures would increase by the same amount, ie 5 degrees C or 9 degrees F. A few decades later, modern climate modeling confirmed that Arrhenius numbers were not too far from truth.

Welcome warming of the Earth

In the 90s, the concept of global warming was still a distant problem and was even welcomed. As Arrehenius himself wrote: “Due to the growing percentage of carbon dioxide [CO₂] in the atmosphere, we can hope to enjoy times with a more balanced and better climate, especially in the colder regions of the Earth. "

In the 30s, one scientist finally began to argue that carbon emissions could have a warming effect. British engineer Guy Stewart Callendar has noticed that the US and the North Atlantic have warmed significantly as a result of industrial revolution. Callendar's calculations showed that doubling the CO₂ in the Earth's atmosphere, it could heat the Earth by 2 degrees C (3,6 degrees F). Until the XNUMXs, he still insisted on warming the planet through the greenhouse effect.

While Callendar's claims were largely skeptical, he at least drew attention to the possibility of global warming. This attention has played a role in commissioning some of the first government-funded projects to monitor climate and CO levels more closely₂.

Keeling curve

The most famous of these research projects was a monitoring station set up in 1958 by the Scripps Institution of Oceanography atop the Mauna Loa Hawaiian Observatory. The local geochemist Charles Keeling developed a device for accurate measurement of CO concentration₂ in the atmosphere, securing funding for this observatory, located in the middle of the Pacific Ocean. Observatory data revealed a phenomenon later known as the "Keeling curve". The rising trend curve with tooth-shaped fluctuations showed a steady increase in CO levels₂. Fluctuations in levels show seasonal oscillations caused by the annual alternation of the winter season and the growing season in the northern hemisphere.

With the beginnings of advanced computer modeling in the 20s, the possible outcomes of rising CO levels began to be predicted.₂, which were evident from the Keeling curve. Computer models have clearly shown that the doubling of CO₂ could cause a warming of 2 ° C or 3,6 ° F in the next century. The models were still considered preliminary and the century seemed to be a very long time.

The threat of the 70s: cooling the Earth

In the early 70s, another type of climate concern emerged: global cooling. More frequent concerns about the pollutants released by humans into the atmosphere have led to some scientific theories that this pollution may block sunlight and cool the Earth.

Indeed, the Earth cooled somewhat in the 1974s and XNUMXs due to the post-war boom of aerosol pollutants that reflected sunlight from the planet. The theory that pollutants blocking sunlight can cool the Earth has taken root in the media, such as in a XNUMX article in Time magazine entitled "Another Ice Age?". But as the short period of cooling ended and temperatures resumed their rising trend, these minority theories lost their relevance. Part of the abandonment of these considerations was the fact that while smog remains in the air for only a few weeks, CO₂ it can remain in the atmosphere for centuries.

1988: Global warming becomes a reality

In the early 80s, there was a sharp rise in global temperatures. Many experts point to 1988 as a critical turning point, with turning points putting global warming at the center of attention.

The summer of 1988 was the warmest on record (although several even warmer ones followed). Drought and large-scale fires also spread in the United States in 1988. Beatings by scientists about climate change has come to the attention of the media and the public. The documents were submitted by NASA scientist James Hansen, who presented his climate models at a congress in June 1988 and said he was "99% sure" that this was global warming.

IPCC - Intergovernmental Panel on Climate Change

One year later, in 1989, an Intergovernmental Panel on Climate Change (IPCC) was established within the United Nations to provide a scientific view of climate change and its political and economic implications.

As global warming gained in importance as a real phenomenon, scientists began to consider its possible consequences. Among the forecasts were warnings of strong heat waves, droughts and devastating hurricanes, rising sea temperatures.

Further studies have predicted the possible flooding of many cities along the east coast of the United States due to the melting of massive glaciers at the poles, which could raise sea levels by 2100 to 28 centimeters by 98.

Kyoto Protocol: US acceptance and subsequent rejection

World government officials have launched discussions to reduce greenhouse gas emissions to try to prevent the worst-case predicted consequences. The first international agreement to reduce greenhouse gases, the so-called Kyoto Protocol, was adopted in 1997. The protocol, signed by President Bill Clinton, committed 41 countries + the European Union to reduce emissions of six greenhouse gases by 2008 percent below of 2012.

In March 2001, shortly after taking office, President George W. Bush announced that the United States would not ratify the Kyoto Protocol. He argued that the protocol "contained fundamental errors" and referred to fears that the agreement would significantly damage the US economy.

Home truth

That same year, the IPCC issued its third report on climate change. It stated that global warming, unprecedented since the end of the last ice age, was "very likely" and had devastating consequences for the future. Five years later, in 2006, former US Vice President and presidential candidate Al Gore drew attention to the dangers of global warming in his film debut "The Unpleasant Truth." Gore then won the 2007 Nobel Peace Prize for his work on climate change.

However, politicking continued in the area of ​​climate change, with some skeptics arguing that the predictions presented by the IPCC and published in the media were, like Gore's film, exaggerated.

Among those who were skeptical about global warming was future US President Donald Trump. On November 6, 2012, Trump tweeted: "The concept of global warming was created by the Chinese to make U.S. production uncompetitive."

Paris Climate Agreement: US acceptance and subsequent rejection

The United States, led by President Barack Obama, signed another milestone agreement in 2015 - the Paris Climate Agreement. In this agreement, 197 countries have committed themselves to setting targets for reducing their own greenhouse gas emissions and to reporting on their progress. The basis of the Paris Climate Agreement was to prevent a global temperature increase of 2 ° C (3,6 ° F). Many experts considered the 2 degree C warming to be a critical limit which, if exceeded, would increase the risk of deadly heat waves, droughts, storms and rising global sea levels.

The election of Donald Trump in 2016 led to the US withdrawing from the Paris Agreement. Referring to the "severe restrictions" imposed by the agreement, President Trump said he could not "in good conscience support the agreement punishing the United States."

In the same year, independent analyzes by NASA and the National Oceanic and Atmospheric Administration (NOAA) found that the Earth's surface temperatures in 2016 were the highest since 1880, when modern measurement methods began to be used. And in October 2018, the UN Intergovernmental Panel on Climate Change issued a report calling for "rapid and far-reaching" action to limit global warming to 1,5 ° C (2,7 ° F) and avert the worst and irreversible consequences for our planet. .

Greta Thunberg and climate strikes

In August 2018, Swedish teenager and climate activist Greta Thunberg began a protest in front of the Swedish parliament, saying: "School climate strike." students in 2018 countries. In March 17, Thunberg was nominated for the Nobel Peace Prize. In August 000, she attended the United Nations Climate Change Summit in New York, famous for crossing the Atlantic by ship instead of a plane to reduce her carbon footprint.

The UN Summit on Climate Action emphasized that "1,5 ℃ by the end of this century is a socially, economically, politically and scientifically safe border" and set a deadline of 2050 for achieving net zero emissions.

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