The scientific notions about climate change that we should all know, in six graphs

At a time when the United Nations climate summit in Scotland (COP26) is putting the focus on policies on climate change and the impact of global warming, it is especially helpful to understand what the science has shown so far.

Soy atmospheric scientist, and for most of my career I have researched and conducted assessments in the field of global climate science. Here are six things you should know about this, with their corresponding charts.

What is causing climate change?

The key issue in the negotiations is carbon dioxide. This greenhouse gas is released with the burning of fossil fuels (coal, oil and natural gas), but also as a consequence of forest fires, changes in land use or generated by sources of natural origin.

The Second Industrial Revolution, which began at the end of the 19th century, caused a huge increase in the burning of fossil fuels. This enabled the powering of homes and industries, and ushered in the era of global transportation.


In that same century, scientists already detected the capacity of carbon dioxide for increase global temperatures, which at the time was thought could even have positive consequences for the planet.

In the middle of the 20th century, systematic measurements began to be made. Since then these have reflected a constant increase in carbon dioxide levels, something that for the most part can be blamed directly to the burning of fossil fuels.

Once it reaches the atmosphere, carbon dioxide tends to stay there for a long time. A part of the CO₂ produced by human activity is captured by plants, and another part is directly absorbed by the oceans. Nevertheless, about half of this gas is trapped in the atmosphere, where is likely to remain for hundreds of years, and from where it exerts its influence on the global climate.

In 2020, during the first year of the pandemic of the coronavirus, when the use of private cars fell and some industries briefly stopped their activity, carbon dioxide emissions from the burning of fuels were reduced by around 6%. But this did not imply a reduction in the concentration of carbon dioxideas the amount released into the atmosphere by human activity still far exceeded what the atmosphere could absorb naturally.

If civilization stopped emitting carbon dioxide today, it would still take several hundred years so that the volume of this gas in the atmosphere would be reduced naturally and the planet’s carbon cycle would return to equilibrium due to the persistence of CO₂ in the atmosphere.

How do we know that greenhouse gases can change the climate?

Much scientific evidence indicates that the increase in greenhouse gas emissions produced during the last century and a half has been the fundamental factor of long-term climate change throughout the world. For instance:

Scientific evidence shows that when carbon dioxide levels have been high, so have temperatures.
Prepared from Salawitch et al., 2017, and updated with data from the end of 2020, CC BY
  • The long-term records of the ice cores, the tree rings and the corals show that when carbon dioxide levels have been high, so have temperatures.

  • Our neighboring planets also offer us scientific evidence. The atmosphere of Venus has a large amount of carbon dioxide and is consequently the planet with higher temperatures of our solar system. And this despite the fact that Mercury is closer to the Sun.

Temperatures are rising on every continent

The increase in temperatures is evident in the records of all the continents, and also in the oceans.

However, temperatures are not rising with the same intensity at all sites. There are numerous factors that condition the temperatures of each region, such as land uses, which influence the amount of solar radiation absorbed or reflected, specific heat sources such as urban heat islands, or contamination levels.

In the Arctic, for example, the rate of increase in temperatures is three times higher than the average for the Earth. In part, this is because, as the planet warms, snow and ice melt, making the Earth’s surface more likely to absorb (rather than reflect) solar radiation. As a consequence, both the snow cover and the frozen seas are shrinking faster.

What is climate change doing to the planet?

The Earth’s climate system is complex and interconnected, so even small variations in temperature can have a big impact (for example, on snow cover or sea level).

And the changes are already happening. There are studies that show how rising temperatures is already having an impact in the precipitations, in the glaciers, in the atmospheric patterns as well as in the incidence of the tropical cyclones and the great storms. Numerous works show, for example, that the increased frequency, intensity and duration of heat waves affect ecosystems, human health and to activities such as commerce or agriculture.

Historical ocean level records have shown almost always increasing increases over the past 150 years. This has occurred simultaneously with the retreat of the glaciers and the general increase in temperatures, which have increased the amount of water in the oceans with some local deviations, as some lands have been submerged and others have risen above the level of the ocean. sea.

Although it is true that extreme weather events have their origin in complex sets of causes, some of these are exacerbated by climate change. In the same way that coastal flooding can be made worse by rising ocean levels, heat waves can be more complex to manage if average temperatures rise.

Climate scientists work hard to assess the changes that will occur both as a result of increased carbon dioxide emissions and due to other expected changes, such as an increase in the global population. It is clear that temperatures will rise, and that precipitation patterns will also vary, but the exact magnitude of these changes will depend on many interrelated factors.

Map models showing estimates of temperature and precipitation volume
Based on SSP3-7.0, a high emissions scenario.
Claudia Tebaldi, et al., 2021

Some reasons for hope

Fortunately, scientific research methods are improving our knowledge of the climate and the complex general ecosystem of our planet, thus identifying the most vulnerable areas and coordinating efforts to reduce the catalysts of climate change.

The efforts being made in renewable energies, in alternative energy sources and in mechanisms to capture the carbon that industries expel into the atmosphere offer new options to societies now better prepared for this challenge.

At the same time, people are learning to reduce their individual climate impacts, as there is growing awareness that a coordinated global effort is necessary to achieve significant impacts. The use of electric vehicles and solar and wind energy is increasing until reaching levels previously unthinkable. And more and more people are willing to change traditional ways of doing things to achieve greater energy efficiency, more sustainable consumption and to consolidate the alternative of renewable energies.

Scientists argue with increasingly strong evidence that abandoning the use of fossil fuels has additional benefits What better air quality, which has positive consequences for both human and ecosystem health.

This article is part of the coverage of The Conversation on COP26, the Glasgow climate conference.

Follow full coverage on English, French, Canadian French, indonesian language and español, here.

Betsy Weatherhead, Senior Scientist, University of Colorado Boulder

This article was originally published on The Conversation. read the original.

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