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Some industrialists are denying increasing accumulation of anthropogenic greenhouse gases.
what was the record of CO2 in Mauna Loa in 1958
what is accounting for our climate change today/
Exceenete tema de discusion
Los aumentos excesivos de CO2 son perjudiciales para el planeta, pero esto puede producirse naturalmente. con gases como el CH4. estos gases han aumentado desde la industrialización, hay varias fuentes para producir esto, no solo la quema de combustibles fósiles, la deforestación y cambio de uso de suelos son los factores que mas se resaltan.
Industrial Age brought increase in carbon from Industrial sector in the 1900s.
What is Environmental Accounting?
There is no doubt that CO2 is accumulating in the atmosphere. The record from Mauna Loa, in Hawaii charts a continuing rise in CO2 concentration since measurements began in 1958, when the level was 315 ppm; the value had reached about 370 ppm by the end of the 20th century, and hit more than 378 ppm in 2004.
Important as changes in atmospheric CO2 undoubtedly are, we need to be aware that this is not the whole story of human-induced greenhouse forcing. In particular, monitoring programmes established during the 1980s reveal an upward trend in the levels of two other natural greenhouse gases as well - methane (CH4) and nitrous oxide (N2O).
The change in atmospheric CO2 during the period covered by the Mauna Loa record shows a rising trend that seems to have started towards the end of the 18th century.
For some 800 years before that, the CO2 level fluctuated little about a mean value close to 280 ppm. Similar patterns are evident for both methane and nitrous oxide. For each gas, the average level over the first 750 years of these ice-core records (i.e. up to 1750) is taken as a measure of its ‘pre-industrial’ concentration.
The increase in the atmospheric burden of these gases since pre-industrial times is not linear, rather it appears to be accelerating. For example, it took over 200 years for the level of CO2 to rise from 280 to 330 ppm (1750 to around 1975); it has taken just 30 years for it to increase by the same amount, i.e. a further 50 ppm.
But how do we know that the build up of all three gases over recent decades is due to human intervention?
One strong line of evidence that it is comes from an unlikely source - the vast ice sheets of Greenland and Antarctica.
As glacier ice is formed by compaction of successive layers of snow, small bubbles of air become trapped. When a sample of ice is drilled out, these air bubbles can be dated quite accurately, and when analysed, provide an archive of past atmospheric composition - including the levels of CO2 , CH4 and N2O.
For the most part, the human impact on the atmospheric burden of natural greenhouse gases can be traced back to activities that effectively add a new source of the gas and/or increase natural emissions in various ways.
In the following pages we will review:
• Carbon dioxide,
• Nitrous oxide, and
Despite being the feature that characterises the industrial age, burning fossil fuels is not the only anthropogenic source of CO2. For centuries, people have been clearing forests, burning the wood and turning vast tracts of land over to agricultural use in order to feed an ever-expanding population. The process of deforestation and land-use change also adds to the CO2 content of the atmosphere.
Methane is generated during the breakdown of organic matter by bacteria that thrive in anaerobic (i.e. oxygen-free) environments - principally in waterlogged soils (bogs, swamps and other wetlands, whence methane's common name of ‘marsh gas’) and in the guts of termites and grazing animals.
Nitrous oxide is part of the natural nitrogen cycle. It is produced by the activities of micro-organisms in soils and sediments. Again, the increase in its atmospheric concentration is thought to result mainly from agricultural activities, such as the application of nitrogenous fertilisers to boost crop yields. Some of the nitrogen ends up in the air as N2O.
In addition, the high-temperature combustion of fossil fuels (or indeed, any kind of vegetation) in air produces some N2O (through reaction between N2 and O2 in the air), along with other nitrogen oxides (notably nitric oxide, NO).
Ozone is also a natural component of the lower atmosphere (due in part to transport down from the stratosphere), but the normal background level is low. However, enhanced concentrations of tropospheric ozone are now found in many polluted environments, especially over densely populated industrialised regions.
Here, ozone is generated close to the surface by the action of sunlight on the mix of gaseous pollutants that is typically found in vehicle exhaust fumes - unburnt hydrocarbons, carbon monoxide (CO) and nitric oxide (NO). Ozone is one of the more noxious components of ‘photochemical smog’ , since exposure to enhanced levels of the gas is harmful to both human health and plant growth.
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