Climate change


Appearing in the media since the 1980s, the term “climate change” has not ceased to provoke numerous debates, due to the occasional skepticism of some regarding the veracity of the existence of climate change.

The greenhouse effect, a natural phenomenon

The greenhouse effect is a natural phenomenon, without which life on earth would be impossible. It is the reason global surface temperatures have increased. Two-thirds of the sun’s energy is absorbed by the atmosphere, soil and oceans. Additionally, infrared radiation is absorbed by clouds and greenhouse gases. It is estimated that without this atospheric greenhouse effect, the average temperature at the surface of the earth would be at most -19° C instead of the 15° C that we know.

Natural Greenhouse Gases – Issues On Climate Change inside Examples Of Greenhouse Gases - World of Examples

Image illustrating the Greenhouse Effect according to the IPCC

Human activities are causing a significant rise in the concentration of greenhouse gases which are transforming the climate at a rate never seen before, leading to a risky imbalance on a global scale.

Past observations

Between 1880 and 2012, there was a 0.85° increase in the Earth’s surface temperatures. In the 20th century, global average temperatures increased by about 0.6 °C, while those of metropolitan France have increased by more than 1 °C. Since 1850, the 10 warmest years on record have occurred after 1998; and during the last 30 years, each decade has been significantly warmer than the prior one. Since the 1950s, the average number of cold days and nights has decreased, while the average number of hot days and nights has increased, along with the frequency of heat waves.

Ocean temperatures have also increased, the most significant warming taking place on the surface. An increase of + 0.11 ° C per decade was observed between 1971 and 2010.

These past observations affect many climatic parameters.

62 years of global warming in 13 seconds (source: NASA)

Scientific opinion

According to IPCC experts, the link between human activities and the increase in temperatures observed since 1950 is extremely likely (95%).  In 2014, the IPCC published its 5th report and proposed new scenarios regarding changes in greenhouse gas emmissions. To analyze the future of climate change, experts at the IPCC have theoretically defined four concentration trajectories for greenhouse gas, ozone levels, aerolsols and land use called RCPs (“Representative Concentration Pathways”).

The RCP 2.6 scenario, which includes a drastic reduction in GHG emissions, is new to this report. This is the most optimistic scenario and the only one that allows for global warming to be limited to +2 °C.

With such an objective, the issue of greenhouse gas emissions is becoming more and more important for countries, and the consequences regarding taxes and legislation are slowly emerging.

This is why, both for reasons of social responsibility and to adapt to new economic and regulatory contexts, it is essential for organizations to engage in the management of their GHG emissions.

Understanding global warming in 4 minutes (source: Le Monde)

Climate projections

The IPCC’s work is based, in particular, on changes to emissions or concentrations of greenhouse gases and aerosols, due to human activities. To make these projections, it is necessary to make assumptions about the evolution of global demography and lifestyles. In their latest report, experts from the IPCC proposed four concentration trajectories regarding GHG, ozone and aerosol emissions and as well as land usage:

The RCP 8.5 is the most pessimistic

RCP 6.0 and 4.5 are intermediate scenarios

RCP 2.6 scenario is unique in integrating the effects of GHG emission reduction policies which limit warming to +2 °C.

The other three trajectories analyzed by the IPCC result in a temperature rise, by the year 2100, of more than 2 degrees when compared to the preindustrial era (1850).

Impacts of climate change

The effects of climate change are already present and could be amplified in the years to come. Many sectors will be impacted:

Biodiversity and water resources:: appearance and disappearance of species, water temperatures, monitoring of water quality, changes to migration areas and wildfires

Agricultre and forestry: increase in the frequency and intensity of drought episodes, emergence of new diseases, changes in leaf and bloom dates, changes in agricultural practices, etc.

Coastal and marine environments: erosion, rises in sea levels and ocean salinity rates, acidification of ocean water and sea surface temperature

Health and population: emergence of new diseases, increase in the frequency and intensity of heat events, pollination

Economic events: changes in activities, natural risks

See map of global warming impacts

Become an agent of change

While the report is alarming, this is not a time for fatalism but for action. The choices that will be made in the coming years in terms of reducing GHG emissions will be decisive ones. Mitigation strategies at all levels, coupled with adaptation strategies, need to be implemented now.

To achieve the goal of staying below 2 °C, global greenhouse gas emissions must be reduced by 40% to 70% in 2050 (compared to 2010 levels), and emission levels will have to be reduced to near zero by 2100. Now is the time to start the transition.

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