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Why is the argument: "the climate has always changed" often seen as relevant?

Climate change, global warming, the impact of greenhouse gases, ... these are all expressions that have been used a lot in recent decades. Although all this semantics points to the same problem, knowledge and understanding do not always follow the same path. For various reasons, there is a difficulty in making climate change understood and/or accepted by some opinions.

In West Africa, memories of the great drought of the 1970s are still vivid in rural areas. Often recounted by some older people, it is seen as a situation that happened in a normal cycle of life; and confirms for them that times have always changed as well as the climate. This example here and this observation are based on a life experience over a short period of time, of the existence of these populations.

Over millions of years the Earth's climate has changed a lot and has always changed. With reference to this knowledge and reality, the issue of understanding climate change today because of human activity arises. Many people argue that the climate has always changed. In addition, there are disinformation campaigns based on the results of climate science. A set of facts that constitute some of the obstacles to understanding human-induced climate change.

The Anthropocene-Pliocene analogy

Indeed, to support arguments about anthropogenic climate change, one of the views of climate scientists is that greenhouse gas emissions are increasing with increasing levels in the atmosphere, particularly carbon dioxide (CO2). Scientists explain that the rate of CO2, which has risen from about 280 parts per million (ppm) in the pre-industrial Anthropocene to 400 ppm in the last two hundred (200) years on our planet, is due to human activities.

This argument is difficult to understand for some people, referring to climate science and making an analogy with the Pliocene (between 5.3 and 2.6 million years ago). Indeed, data from sediment samples about four million years old suggest that carbon dioxide was at 400 ppm in that era.

Thus, if CO2 levels reached 400 ppm about four million years ago, a period geologically quite close to our own, and without any anthropogenic sources, then by referring to this Anthropocene-Pliocene analogy, some of the public believe that this phenomenon is not new and cannot justify the current climate change.

However, this analogy is not relevant because the Pliocene climate was balanced at all levels in this era with, of course, 400 ppm CO2 but a higher sea level of between 15 and 20 meters and smaller ice caps in Greenland and West Antarctica. This is not the case now in our era, in the climate situation on earth.

Planet Earth is 3 degrees cooler

Another point of misunderstanding on the issue of climate change is the rise in the Earth's temperature. We also know that in the Pliocene the average temperature on Earth was 3 to 6 degrees Celsius higher than today, with warmer summers (up to 14 degrees Celsius) in the high northern latitudes. This still raises the question in some quarters as to how scientists can claim that we are experiencing global warming while ignoring the warmer periods of the past.

The explanation of the problem of change by the thesis of global warming is also misunderstood in reference to the cold spells of recent years on the American continent. For some, this proves that there is no global warming. However, this is not a valid reasoning because these phenomena can simply be explained by polar air descending and cannot justify that there is no global warming.

Modelling and weather are unreliable

Access to temperature data by scientists prior to 1980 was limited because they had little or no capacity for satellite measurements. Temperature curves from before these years were therefore controversial. This has led to misunderstandings of the climate change arguments based on modelling.

If we are wrong about the weather of the coming days, how can we predict the climate of future decades? This question is often the basis of misunderstandings about the phenomenon of climate change predicted by climate science. However, even if it is not easy to predict the weather accurately in a week, it is certain that July will be warmer than December in a year. For these physical reasons and because of CO2, it is possible to predict climate change.

Greenhouse gases prevent the earth from cooling

Part of the energy released by the planet Earth in the form of radiation goes back into space through the atmosphere. This energy is accumulated by the gases in the atmosphere and then partly returned to the earth. This process, called the greenhouse effect, is very natural and linked to our atmosphere. This is very beneficial because the earth would be much colder without this phenomenon and would not be habitable.

The greenhouse gases thus prevent the earth from cooling down. However, by increasing the concentrations of gases in the atmosphere, the phenomenon is activated, and this has the effect of warming the planet beyond a balanced threshold. This causes climate change.

The increase in the greenhouse effect due to man-made emissions upsets the Earth's energy balance and leads to an overall increase in the Earth's temperature.

It was assumed that the world's oceans had enough absorption capacity to ensure that human-induced carbon dioxide emissions would not have any impact. But it became clear that anthropogenic CO2 releases were increasing its atmospheric concentration and that the oceans did not have the capacity to do so.


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