Forget approximate climate models, whose simulations are increasingly removed from reality. There's a far more scientific way of understanding the climate, and that involves observing the actual climate system directly from space or in situ. A multitude of satellites and a worldwide network of land, air and sea sensors make millions of observations every day, creating detailed, faithful images of the Earth. In particular, satellites transmit huge volumes of data on the upper atmosphere and the Earth's surface, enabling us to measure the system's energy balance and attribute infrared emissions to particular atmospheric components. This high-quality space and in-situ data is freely available to all thanks to Copernicus, but the problem is that we don't use it...

Forget proxies and old data that are constantly being "adjusted". We have proven, measured information that allows us to go back in time to 1960. It's a happy coincidence that January 1, 1960 is the reference 0 for the temperature series commonly used. The IPCC has arbitrarily ruled that climate change began with industrialization, i.e. around 1850 or 1880, since it assumes that GHG emissions are the cause. But data from the world's oceans, which drive climate, show that their temperature began to diverge from its natural cycle around 1980. So let's focus on the last sixty years, using the real-world observations available to objectively identify the true culprits of anthropogenic warming.

This heterodox but oh-so-interesting point of view is supported by space engineer Michel Vieillefosse, a pioneer in satellite auscultation of the Earth. At CNES, he produced the first maps of thermal variations measured from space. His recent book " Réchauffement climatique" is a mine of information on the climate, how it works and its recent evolution. Based on real data and calculations, rather than model projections, he concludes that there's no point in demonizing fossil fuels, and that the real causes of global warming - deforestation of tropical forests, urban heat islands and methane leakage - should be tackled first. Let's see how he arrives at this astonishing conclusion.

Warming is heterogeneous and multi-causal

Since 1960, the global average temperature has risen by 0.9 oC. However, this parameter cannot account for climate change, as it masks the significant disparities in local temperatures over time and space. At best, the average temperature indicates a trend.

Contrary to the impression created by the term "global warming", climate change is far from uniform. The warming picture looks more like a patchwork quilt than a blanket. It is therefore essential to look at each region individually, and see what is really happening there, if we are to understand the climate scientifically. All these heterogeneities that blend into the average have a specific explanation.

The Arctic is warming by 2, 3 or even 4 times more than the rest of the globe. This amplification observed since 1990 is mainly due to the influx of warmer waters from the tropics via the great oceanic heat conveyor, replacing the cold waters carried towards the Equator, and to the virtual absence of evaporation and lower albedo. It's worth noting that an initial warming attested in 1938, 1943 and 1944 was followed by a cooling period.

No such increase is observed in Antarctica, isolated by a circumpolar current. It does not change as a whole. The fact that Antarctica has hardly warmed at all since 1960 is a pebble in the shoes of the carbocentrists who blame everything on CO2 (being a well-mixed gas, its effect should be felt everywhere).

The obsession with GHGs has made us forget how the climate system really works. While the sun is the only real source of heat, the Earth cools not only through infrared radiation to space, but also through convection, evaporation and plant transpiration. Let's understand that these mechanisms act as heat elevators; they cool the lower atmosphere; infrared radiation then takes over to evacuate the heat into the void; ironically, it's mainly CO2 that takes on this task in the absence of high-altitude water vapour. Consequently, human activities that interfere with these mechanisms, such as deforestation and urbanization, cause marked local warming... but this is overlooked by the IPCC and climate models.

Three case studies are presented in M. Vieillefosse's book to illustrate the impact of these interferences on climate: Hawaii, Beijing and Manaus, with respective temperature anomalies of 0.4°C, 1.9°C and 1.5°C since 1960. Such large discrepancies, in contradiction with atmospheric mixing, must lead us to investigate their specific causes: little human intervention for Hawaii, a vast urban footprint for Beijing and reduced vaporization of the Amazon rainforest for Manaus.

Let's not lose sight of the fact that excess local heat that is not evacuated into the vacuum of space is eventually absorbed by the global ocean, whose thermal storage capacity is 1,000 times greater than that of the atmosphere. Basic physics says that oceans warm the atmosphere, not the other way around. The warming ocean enigma is thus solved.

The contribution of CO2 is secondary

CO2 levels have risen by some 140 ppm to 418 ppm over the past 60 years. According to ERBE satellite data, this increase has blocked 1.42 W/m2 of energy, which translates into a 0.21°C rise in the temperature of the lower atmosphere. Compared with the total CO2 contribution of 48 W/m2, this represents only 3% more. CO2 emissions resulting from human activities are therefore not the primary cause of climate change. On the other hand, they are clearly responsible for the greening of the Earth revealed by NASA satellites, a huge benefit for the planet, but this not recognized for its true value.

Similarly, methane has risen from 1.36 ppm to 1.86 ppm, for a forcing of 0.46 W/m2 ; this blocking of infrared radiation has led to a temperature rise of 0.06°C, which is therefore minimal. But with the increasing use of shale gas and the proliferation of landfill sites, methane emissions are on the rise.

Both tropospheric and stratospheric ozone also play a part in blocking infrared radiation emitted into space, but the latter also plays an indispensable role in blocking harmful UV rays.

Of course, water vapour is primarily responsible for the greenhouse effect, but it is also the main vector of cooling, of an order of magnitude incommensurate with infrared radiation. Its importance for the climate of our "blue planet" is immense but ignored. Man's activities have reduced natural evaporation in the tropics; heat accumulates in the oceans and is transported to the North Pole, where it can only be evacuated with difficulty, hence the overheating of the Arctic. Contrary to what the models and those whose livelihoods depend on them imply, we have not observed any significant increase in water vapour in the atmosphere (prior to the Hunga Tonga eruption).

Tropical forests, the Earth's radiator

Satellite measurements show that tropical rainforests (6.25 million square kilometers, or around a third of the world's forests) have an average cooling effect of - 2.4°C on the ground, compared with cultivated areas. At mid-latitudes, the effect is much less marked, if not non-existent. By contrast, boreal forests above 50° latitude have a local warming effect of +0.8°C.

Concentrated in South America, Asia and Africa, tropical forests act as the Earth's radiator, absorbing solar radiation, cooling it through evapotranspiration and providing water vapour for cloud formation.

The Amazon represents the heart of our planet's transpiration system. Because of its dark color, the forest captures more solar radiation than other soils. But this energy is returned by evapotranspiration, then rises into the upper layers of the atmosphere by convection, and finally radiates out into space. The air above the canopy contributes to cooling the whole Earth. The Amazon pumps and releases around 20 billion tonnes of water a day into the atmosphere. The Amazon creates 75 % of its own rain.

Deforestation reduces emissivity by 10%, or 36 W/m2. For the globe as a whole, the figure is 0.17 W/m2. But what's more serious is the suppression of evapotranspiration, in the absence of trees. Latent heat loss rises to 0.78 W/m2, spread across the globe. We lack 480 million hectares of forest to evacuate around 1,000 mm of water a year, along with the heat required for evaporation. This disrupts the precipitation cycle.

Some 240 million hectares of forest were cleared between 1990 and 2015. Roughly the same amount of woodland is likely to disappear by 2030, equivalent to 1/200 of the earth's surface. As we are constantly told, this has the effect of releasing the carbon dioxide stored in trees and forest soils. But carbo-centrists forget that the main impact of deforestation is to deprive the Earth of a powerful cooling mechanism.

In total, deforestation has caused half of the temperature rise since 1960, or 0.46°C, twice as much as CO2. Although never mentioned in the media, it is the main cause of climate change. And things aren't getting any better.

Rapid urbanization: a significant factor

Today, 56% of the world's population, or 4.4 billion people, live in cities. This trend is set to continue: by 2050, with the current number of city dwellers doubling, almost seven out of every ten people in the world will be living in urban areas. While it's true that cities account for only a tiny fraction of the Earth's surface - 1/1000 - land artificialisation and other urban interference create heat islands, with temperatures up to 10°C higher than in the surrounding countryside. These are concentrates of climate change!

Increasingly mineralized urban areas use dense building materials, eager to absorb the sun's energy. With less vegetation, they provide less shade and do little to cool spaces, notably through evapotranspiration. Depending on their morphology, buildings can also prevent the wind from circulating and cooling the streets. In addition, waste heat from car engines, air conditioners and other energy-guzzling appliances adds to the overall rise in air temperature.

Urbanization increases the absorption of solar radiation, but above all it weakens the infrared radiation emitted by surfaces; emissivity can drop to 50%. This drop in emissivity results in more heat being retained at ground level, in excess of 180 watts per square metre, hence the famous "heat islands". Black tar roads absorb even more solar heat. Rapid urbanization blocks soil transpiration. We see as much less cooling of the planet; the impermeabilization of surfaces immediately washes rain into watercourses via stormwater networks.

All in all, urbanization generates warming of the same order of magnitude as that created by CO2. It is also responsible for flooding.

Action to counter global warming

Following the Kyoto and Paris Agreements, the fight against climate change is almost exclusively focused on reducing CO2 emissions. Unfortunately, we've got the wrong target. If we reduce anthropogenic CO2 emissions to zero, its concentration will fall by just 2.5% per year. In other words, nothing. Let's not forget that the drastic reduction in carbon emissions during the 2020 confinements did nothing to slow the rise in CO2 levels, or in temperatures, and this was due to concomitant phenomena. What's the point of cancelling CO2 emissions at a huge cost if temperatures continue to rise?

In the case of methane, on the other hand, it would be relatively easy to plug the main leaks, which are easily identifiable. The fight against methane involves controlling open-air landfills and gas installations, which are responsible for 40% and 26% of emissions respectively. Dairies and composts emit 26%. Doing without milk seems difficult. We need to act first on the first two, less natural causes. So let's introduce a methane tax... instead of this ineffective carbon tax!

But above all, let's stop focusing on CO2 and tackle the human activities that cause most of the warming. Priority should therefore be given to preserving tropical forests, especially the Amazon. If the entire Amazon rainforest were to be chainsawed, it would be a global ecological disaster, both in terms of climate and biodiversity. The Amazon would become nothing less than a desert, which is all the more plausible given its location in the "right" band of latitudes. Putting an end to deforestation now would make a tangible contribution to mitigating global warming. Why not set up a global fund for the conservation of tropical forests... instead of financing anti-oil activists? Therein lies the urgency of action to save the planet.

We can't stop urbanization, but we can start to think differently about cities and buildings. Interesting experiments are being conducted here and there, notably to combat those pesky heat islands. It's in cities' own interests to take action, because it's first and foremost they themselves who will reap the rewards of their actions.

We also need to adopt a more rational, non-ideological approach to energy transition, especially in Europe. Haste is also a bad advisor. So-called renewable energies have reached their limit in Germany. Sun and wind alone cannot replace fossil fuels. Innovation will be key in the future, as it has always been in the history of mankind.

Mr Vieillefosse's book concludes as follows: Isn't it time we looked at the problem from a scientific rather than a political angle, and took rational, effective measures rather than acquiescing to sad demagoguery? May this book open the fight against global warming to a plurality of possible solutions.

May his wish come true. At any rate, it's worth saving the Amazon and reducing urban heat islands.
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