Climate change is a reality. The climate has been changing abruptly for several decades and the effects of that change are already beginning to be felt. In each place they occur in a different way, but they have an impact on a planetary scale. Changes in temperature, alteration of the seasons, increase in the magnitude and frequency of extreme weather events… Of all these, the effect that is easiest to measure is what we know as global warming . And it is that one of the traces of climate change is, indeed, the increase in the average temperature of the planet .
The climate: a changing entity
It is true that the climate is not a static entity, but a changing one. It has changed in the past and it will change in the future . We know that today’s climate is not the same as the one during the Würm glaciation 80,000 years ago, much less the Triassic, the Carboniferous or the Ordovician.
The climate alternates periods of certain stability with periods of change , in a frequency that is not periodic, and whose events can be triggered by multiple causes: an increase in volcanism, an inversion in the Earth’s magnetic polarity, an increase or decrease in radiation. solar; even the impact of a meteorite can lead to climate change that, sometimes, becomes catastrophic.
The global warming observed today is the most abrupt and rapid of all the changes that we are aware of , and it correlates precisely with an increase in industrial activity, particularly with the massive burning of fossil fuels, something that is can be quantified by checking the concentration of carbon dioxide in the atmosphere.
This event does not seem like a coincidence, but these types of correlations must be taken with caution. We often find coincident events in time that do not always have a direct cause and effect relationship ; In other words, a correlation does not always imply causation. To accept that there is a cause and effect relationship, it is necessary to check it. There are many other variables that may be affecting the climate, and not all of them have an anthropic origin.
Is climate change caused by the sun?
One of the ideas that circulate about climate change is that it is a phenomenon caused by solar activity , and that human beings have not had any responsibility —nor do they have solutions in their hands to mitigate it—.
The sun has several types of cycles in which its activity varies . Some are very fast cycles — barely a decade long — and so insignificant that their effect does not affect the Earth’s climate. But others are much longer cycles and of greater magnitude. It has been possible to study, indirectly, the intensity of the solar radiation that the planet has received in the last 8,000 years, and it has been found that there are other particularly significant cycles, one that occurs approximately every 75 years, and another every 200 years.
The records show us that this type of solar cycles could be the cause of certain climatic minimums that run through our recent history. These are the cases of the Maunder minima, between 1650 and 1700; or Dalton’s, between 1790 and 1820. However, these cycles rule out that the sun is the cause of global change; there was a maximum position of the cycle in the middle of the 20th century, but currently, and since 2008, we are in an event of minimum activity, so the sun, at this time, far from causing global warming, is slowing it down.
The cause-effect relationship
The correlation between temperature and CO₂ is a relationship that dates back to prehistory as far as it can be studied —these are data that can be studied thanks to the study of ancient ice. Periods of maximum temperatures correspond to periods of high atmospheric carbon concentration, and vice versa.
It is proven that the causal relationship exists . Carbon dioxide, like methane, water vapor, and other gases, plays a role in the well-known greenhouse effect. It retains the infrared radiation that is emitted by the earth into space by absorbing sunlight, and heats the environment, similar to how glass works in a greenhouse. However, how can we be sure that this carbon originates from human activity, and is not part of other sources, such as volcanism?
Thanks to studies with carbon isotopes, we know that the excess of CO ₂ comes mainly from living beings , and not from other sources such as volcanism, whose contribution to climate change is minimal.
Of course, the respiration of living beings or fires could be the cause, but those same studies with carbon isotopes show that the CO₂ that makes up the excesses that we observe in nature, that CO₂ that is behind climate change does not come from of modern living beings, but of fossil organisms. Living beings that obtained their carbon by photosynthesis hundreds of millions of years ago , and that today we are releasing. Those prehistoric living beings, plants and algae, that formed what we know today as coal, oil and natural gas .
This is how we know that climate change is anthropogenic in origin. And in this regard, the consensus in the scientific community is overwhelming .
References:
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