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Climate Change: Answers to the Key Arguments of the Deniers

Sunday, 22.09.2019
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Reporting on climate change is one of the major journalistic challenges of our time. The climate crisis is also one of the most important issues of humanity for SPIEGEL. For this reason, we support an international initiative that seeks to take a look this week: "Covering Climate Now" was initiated by the Columbia Journalism Review and the Canadian newspaper "The Nation", with more than 200 media companies around the world, including the Guardian, El País, La Repubblica, The Times of India, Bloomberg or Vanity Fair. SPIEGEL is dedicating the cover story of the current issue to the climate crisis this week and every day pays special attention to mirror.de

  
Myth 1: Climate change has always existed

  
  

Little time? At the end of the section's a summary.

  
  That's true. However, the statement does not refute that human emissions also influence the climate. And after all that is known today, man-made climate change is fact. Thus, studies of earlier hot and cold times show that they differed significantly from the current rise in temperature.

  

In July 2019, researchers showed in several studies in the journals "Nature" and "Nature Geoscience" that the Earth's climate has never warmed in as many places at the same time as it does over the past two millennia. This resulted in analyzes of old tree trunks.

  
At the beginning of the small ice age, which ruled from the 15th century to the 19th century, temperatures initially dropped the most in the Central and Eastern Pacific. It was not until the 17th century that northwestern Europe and southeastern North America were hit hardest.

  By comparison, the current temperature increase affects 98 percent of the earth's surface at the same time.

  

  

Climate extremes, which are significantly further in the past than the last two thousand years studied, differed from the current climate change: In the Paleocene / Eocene temperature maximum about 56 million years ago, global temperatures rose by about six degrees. The Arctic Ocean had at times 23 degrees Celsius on the surface.

  The decisive difference to today: The climate changed at that time over a period of several thousand years. At last, global temperature has already risen by about a degree within a good hundred years – and warming has developed in parallel with increasing CO2 emissions.

  

  
In summary: It is true that the climate of the earth can change without human influence. But the key question is whether the current change is natural. The rate of temperature rise and its global scale are against it. In addition, climate simulations show that it would be colder without the man-made CO2 emissions on Earth.

  

  
Myth 2: The amount of CO2 in the air is far too low for the gas to have any effect

  
  

Little time? At the end of the section's a summary.

  
  That sounds logical, because in principle: The dose makes the poison and the atmosphere consists only to 0.04 volume percent of carbon dioxide (CO2). By far the largest share is nitrogen and oxygen (see chart below). And yet CO2 is crucial for the temperatures on earth.

  

This is because carbon dioxide, as a greenhouse gas, unlike nitrogen, oxygen and the third most abundant air constituent, argon, can absorb heat radiation. When it comes to how much heat is stored on the earth, the three most important substances in terms of volume are therefore irrelevant. This makes CO2 the most important substance in this regard.

  

  At first, the earth becomes warm only because the sun shines on it. But that is not enough to create pleasant temperatures for us. Without the heat-storing molecules in the atmosphere, much of the solar heat would simply re-radiate back into space. Instead of 15 degrees Celsius, the average temperature on our planet would then be about minus 18 degrees Celsius.

  As a greenhouse gas, CO2 is able to absorb some of the radiated heat and send it back to the ground. As a result, the temperature on the earth rises and brings the greenhouse effect in motion: the heat evaporates strengthened water on the ground. Clouds form, which also prevent heat escaping into space.

  

  If the CO2 content in the atmosphere increases, this effect is intensified – even if the proportion of air in the air remains low overall. The fact that the earth heats up with an annual output of currently about 37 billion tons of CO2 therefore seems plausible. The US ocean authority Noaa alone accounts for 81 percent of global warming, with other human-produced greenhouse gases such as methane.

  
In summary: The CO2 content in the atmosphere is actually low. But because CO2 is the most common greenhouse gas, it has a major impact on the climate. By absorbing in part the heat radiated from the earth towards the universe and sending it back to the ground, carbon dioxide raises the temperatures there. As a result, more water evaporates on Earth and more clouds form, which in turn keep the heat in the atmosphere. The effect is so great despite the comparatively low amount of CO2 that it makes the earth life-friendly in the first place. If the CO2 content rises too much, it will be uncomfortable.

  
Myth 3: Even climate researchers disagree on whether man-made climate change exists

  
  
Little time? At the end of the section's a summary.

  
  Not correct. Almost all researchers who publish on climate change in recognized journals are convinced that warming is driven by humans. An overview study from 2016 showed that 97 percent of recognized experts consider climate change to be man-made. In other words, only three percent doubt it.

  The basis for the number provided the evaluation of more than 4000 studies in which researchers had positioned themselves to the question.

  How large the approval in the professional community is, also the reports of the IPCC show. The Weather Organization of the United Nations (WMO) allows all climate experts to contribute to the report. The IPCC's fifth progress report from 2013/2014 involved more than 830 experts.

  

  Although compromises are common to so many authors, the report concludes that human impact of 95 to 100 percent is the main cause of the current global temperature rise.

  

The federal government even recently reported that more than 99 percent of scientists who publish papers on climate change consider warming man-made. In doing so, she refers to two studies by geologist James Powell (here and here), which came to the fore in the evaluation of tens of thousands of expert opinions reviewed by the expert community. Whether his methodology provides reliable figures, is in the professional world, however, controversial.

  Detail on the edge: The statement of the Federal Government served in response to a small request of the AfD, which had expressed doubts at the 97-Prozent-Unterstützung.

  
In summary: Although experts still disagree whether 97 or more than 99 percent of climate experts are convinced that climate change is man-made, it is clear: it is the vast majority. In the latest IPCC Assessment Report, 830 climate experts agreed that human impact is the main cause of global temperature rise with 95 to 100 percent certainty.

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