Key words: global warming, climate, human activities, consequences, temperatures, ecosystem, global.

Read the 1 part: definition of greenhouse effect

Role of human activity in the greenhouse effect

Most greenhouse gases (GHGs) are of natural origin. But some of them are only due to human activity or see their concentration in the atmosphere increase due to this activity. This is the case in particular for ozone O3, CO2 and methane CH4.

The proof that the increase in atmospheric CO2 is of human origin is done by isotope analysis

The combustion of fossil carbons such as coal, lignite, petroleum or natural gas (methane) releases large quantities of CO2 into the atmosphere. So that only half is recycled by nature, and the other half remains in the atmosphere, which obviously increases the greenhouse effect.

Human activities therefore release an abundance of GHGs: scientists who study the climate believe that the increase in the levels of gases of anthropogenic origin is the cause of global warming.

What consequences for the planet?

The greenhouse effect is not, in essence, harmful to ecosystems: indeed, without it, the Earth's temperature would be around -18 ° C. However, an excess of GHGs could prove to be harmful.

The increase in temperature would first cause a mechanical increase in the volume of seawater by expansion and by the melting of glaciers (and not icebergs), which would engulf part of the land (coral islands, such as the Maldives are the first threatened), would endanger many species and could be at the origin of the degradation of the first "lung" of the Earth: the phytoplankton (producing 80% of the terrestrial oxygen and absorbing a not insignificant part of dioxide of carbon).

Other consequences such as the increase in rainfall or the modification of sea currents could be disastrous. Consequences that are more or less difficult to predict risk causing real climate change.

Scientists predict an increase of 1,5 ° C to 6 ° C (such a margin of error actually means: we don't know exactly!) For the next century assuming that the increase in GHG emissions continues over the next century. current pace. However, stopping carbon emissions altogether would not prevent the average temperature of the planet from continuing to rise for several tens or even hundreds of years.

Indeed, GHGs only disappear from the atmosphere very slowly (See: Greenhouse effect, definition of GWP)

Controversy and scientific debates on the origin and consequences of the greenhouse effect

Studies on global warming and its consequences have been among the most extensive in interdisciplinary scientific history. However, political pressures and the potential consequences for the industrial lobby linked to the exploitation of fossil fuels, which the adoption of carbon emission quotas would dangerously threaten, have favored the emergence and development of a scientific counter-current. questioning the interpretation of the data.

The type of scientific counter-expertise brought against the alarmist theories of the anthropogenic origin of global warming is questionable, in particular because of the funding of these counter-assessments by industrial lobbies, headed by Don Pearlman (cf. Carbon Club). during the agreements signed in Kyoto.

In the video documentary The Greening of the Planet Earth (broadcast in 1988), the Western Fuels Association predicts that the doubling of carbon emissions, as it is underway, would allow an increase in cultivable land on the planet. The Western Fuels Association also funded the launch of the World Climate Review, the content of which can hardly claim the independence that scientific objectivity demands.

Some scientists, while acknowledging the changes brought about by rising sea levels and the need for action, reject the current catastrophism. For example in the case of the Maldives, which are coral islands, the hypothesis according to which the corals are quite capable of raising the islands faster than the rising waters is sometimes advanced. Species would then be led to regress or disappear, while others would appear and develop according to the principles of natural selection. The history of the Earth indeed shows that there have already been in the past periods when it was much hotter and other periods when it was much colder, and that each time nature has found the appropriate answers. Others respond to the same arguments that these transformations have lasted for millennia, while envisioned climate change would occur over a century or two, which may be too fast for nature to adapt.

More:
- The extinction of the Permian
- Road transport and global warming: greenhouse effect.
- Transport and climate change by Climate Action Network France and WWF.
- CITEPA: Inventory of greenhouse gas emissions in France under the United Nations Framework Convention on Climate Change
- CITEPA: Inventory of atmospheric pollutant emissions in France - Sectoral series and extended analyzes