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What Is Global Warming?

In climatology the term global warming indicates the change in Earth's climate developed in the 20th century and still ongoing. This change is largely attributed to emissions into the Earth's atmosphere of increasing amounts of greenhouse gases, and other factors that the scientific community has detected as attributable to human activity.

What is global warming?

Over the course of Earth's history, there have been several variations in climate that have led the planet to cross different ice ages alternated with warmer periods called interglacial ages. These variations are mainly due to periodic changes in the orbital design of our planet, with disturbances due to the periodic development of solar activity and volcanic eruptions (due to CO 2 and dust emissions ).

Recent global warming 

By global warming we mean an increase in average temperatures on the Earth's surface that cannot be traced back to natural causes and was found since the early 1900s. According to the 2007 Intergovernmental Panel on Climate Change (IPCC) fourth report, the average temperature of the earth's surface increased by 0.74 ± 0.18 ° C during the 20th century. Most temperature increases have been observed since the mid-20th century with a distribution of global warming that is not uniform across the world, but peaks in the northern hemisphere from mid to high latitudes to the north pole, more accentuated on land than in the seas and oceans (for example, Siberian and Canadian territory) and a lower level in the southern hemisphere, surrounded by oceans,

This global average increase would be attributable to the increase in the atmospheric concentration of greenhouse gases, in particular carbon dioxide, therefore, a consequence of human activity, in particular the generation of energy by fossil fuels and deforestation, which at the same time it generates an increase in the greenhouse effect. L 'global darkening, caused by increased concentration in the atmosphere of aerosols, which blocks the sun's rays. So, in part, it could mitigate the effects of global warming. IPCC reports suggest that, during the 21st century, the Earth's average temperature may increase further compared to current values, by 1.1 to 6.4 ° C more, depending on the climate model used and the emissions scenario.

Rising temperatures are causing significant ice losses and rising sea levels. The consequences on the structures and intensity of precipitation are also visible, with consequent changes in the position and size of subtropical deserts.

Most forecasting models predict that warming will be greatest in the Arctic area and lead to a reduction in glaciers, permafrost and frozen seas, with possible changes in the biological network and agriculture. Global warming will have different effects from region to region and its local influences are very difficult to predict. As a result of increased carbon dioxide in the atmosphere, the oceans could become more acidic.

Thermal evolution on other planets of the solar system 

It has recently been suggested that some of the planets and satellites in the solar system will experience an increase in temperature. On Mars, the alleged temperature rise stems from an article studying the relationship between sandstorms and surface albedo, and is based on only two points, in 1977 and 1997. An analysis of all available data shows a erratic temperature trend, with no tendency to heat up, and in 2001 the global temperature of Mars was lower than in 1977.

Some models predict an increase in the temperature of the planet Jupiter by approximately ten degrees in the equatorial areas, after an increase in meteorological activity, but not an increase in the average temperature. Furthermore, it is a forecast, not directly observed. On more distant planets like Uranus, Neptune shows temperature increases, but it is likely to be a seasonal variation. We know next to nothing about the meteorology of these planets, which have been observed for a limited time. The hypothesis that these variations are due to variations in solar activity is in contrast to the very weak variations measured for solar irradiation.

Scientific study

The scientific study of current global warming carried out by the scientific community (IPCC climatologists) is carried out through two different procedures: on the one hand, we analyze the significant measurable scientific data for the so-called detection or reference parameters of the causes mentioned above (air temperature). , ocean temperature (SST), solar activity, concentrations of greenhouse gases) to verify the long-term trend of warming or not (analysis of historical series), on the other hand, simulation climate models are used that take into account more or less of all the factors involved in the regulation of the climate system that is constructed from knowledge of the state of the art of climate operation taking into account the physical laws (for example irradiation) and feedback processes. The models, once built, are validated on the basis of past climate data by applying the model to past times and verifying the goodness or otherwise of the simulated climate with the actual past.

These simulations allow us to highlight the causes of climate change and operate future forecasts. Future projections are often called "scenarios" as they take into account various possible levels of carbon dioxide concentration depending on the economic development of different countries on Earth. These models have often been criticized by so-called skeptics / deniers of climate change, as they could not faithfully reproduce the climate system in all of its physical processes, including feedback. Models in the 2000s, in addition to a progressive increase in global average temperature, also provide an increase in the water cycle with an increase in extreme events or droughts and floods, something that has been partially confirmed since the 2010s .

A major problem in climate research related to global warming is the so-called "doubling problem" of the concentration of carbon dioxide in the atmosphere, first studied by Syukuro Manabe with his own GFDL climate model. This problem is also known as the climate sensitivity problem, or the climate system response to carbon dioxide doubling that models do not calculate a priori, but for which a value of a multiplier parameter must be entered. This value is not precisely known, but there are more or less accurate estimates. Another source of uncertainty is the so-called parameterization.

Causes of global warming

Recent climatic changes have been analyzed in more detail only since the last 50 years, that is, because human activities have grown exponentially and observation of the upper troposphere has been possible. All the main factors to which climate change is attributed are related to human activities. In particular these are:

  • Increase in the concentration of greenhouse gases in the atmosphere.
  • Changes in the Earth's surface such as deforestation.
  • Increased aerosols
  • Intensive breeding

A report by the Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed temperature increases since the mid-20th century are likely due to the increase in man-made greenhouse gases; while it is highly unlikely (estimated to be below 5%) that climatic increases can be explained using only natural causes. Warming affects both the ocean and the atmosphere.

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Last review: July 5, 2019