Climate change: Difference between revisions

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Revision as of 14:38, 14 January 2002 view sourceSJK (talk \| contribs)Extended confirmed users, Pending changes reviewers, Rollbackers6,145 edits made the explanation of the UNFCCC and the Kyoto Protocol more accurate← Previous edit		Revision as of 15:23, 14 January 2002 view source Eloquence (talk \| contribs)Extended confirmed users17,329 edits removed non-NPOV characterization of Lomborg ("Lomborg discovered that ")Next edit →
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	] (author of ]) is a Danish professor, ex-Greenpeace, that seems to represent only himself. It can be pointed out that professor Bjorn Lomborg is looking for fame and fortune. His US book presentation on Capitol Hill has been sponsored by the "Competitive Enterprise Institute", an industry-funded "think tank". On the other hand, Lomborg, himself a card-carrying green activist and professor of statistics, set out to disprove a critic of the movement, and discovered to his surprise that much of what many accept as "fact" appeared to be based on mistakes, misquotations, and junk science.		] (author of ]) is a Danish professor of statistics, ex-Greenpeace, that seems to represent only himself. It can be pointed out that professor Bjorn Lomborg is looking for fame and fortune. His US book presentation on Capitol Hill has been sponsored by the "Competitive Enterprise Institute", an industry-funded "think tank".

Revision as of 15:23, 14 January 2002

Global warming is a world-wide climatic phenomenon--the average global surface temperature increased over the last 150 years.

Whether this increase is significant or not is subject to debate. Natural and anthropogenic (man-made) causes were proposed to explain the phenomenon.

Scientists generally believe that increased concentrations of anthropogenic greenhouse gases in the atmosphere, which causes more of the energy radiated from the Sun to be absorbed by the Earth (through the greenhouse effect), play an important role in global warming.

The main evidence for global warming comes from thermometer measurements from land stations all over the world since 1860. The data, corrected for the urban heat island effect, shows that the average surface temperature has increased by 0.6±0.2 C during the 20th century. Most of the warming occurred during two periods: 1910 to 1945 and 1976 to 2000. (Source: IPCC).

Secondary evidence comes from observed variations on the snow cover and ice extent, global average sea level, precipitation, cloud cover, El Nino and extreme weather events during the 20th century. For example, satellite data shows a 10% decrease of snow cover since the late 1960s. The Northern Hemisphere spring and summer sea-ice extent has decreased by about 10% to 15% since the 1950s and there has been a widespread retreat of mountain glaciers in non-polar regions during all the 20th century. (Source: IPCC).

Causes

Climate changes occur due to internal and external factors. Internal factors are factors associated with the complexity of the climate systems which are chaotic non-linear systems. External factors can be natural factors and anthropogenic factors. The main natural external factor is the solar radiation variability. The solar radiation can change because of the solar cycles and because the Sun is getting hotter. Anthropogenic factors are related to changes in the environment influenced by Man. The main anthropogenic factors are the emission of greenhouse gases, the depletion of stratospheric ozone, the land use and the emission of aerosols such as sulphates. (Source: IPCC)

Scientists agree that internal factors and natural external factors can cause significant climate changes.

In the last millennium, two important periods occurred: a warm period known as the Medieval Warming Period and a cold period known as the Little Ice Age.

These periods have a magnitude similar to the current warming and it's agreed that they were cause by internal factors and natural external factors only.

The Little Ice Age is usually attributed to the reduction of solar activity.

Some scientists have claimed in the past that the observed warming since 1860 is a natural climate recovery from the Little Ice Age.

(Source: The Skeptical Environmentalist)

However, large amounts of anthropogenic greenhouse gases were emitted to the atmosphere since the beginning of the industrial revolution. Since 1750, the carbon dioxide concentration has increased by 31%, methane has increased 151%, nitrous oxide has increased 17% and tropospheric ozone has increased 36%. (Source: IPCC)

The majority of these gases are produced by the combustion of fossil fuels.

It is thought that the reduction in tropical forested area has also played a role, as old forests store large amounts of carbon.

However, growing forests in North America and Russia contribute to absorb carbon dioxide (they act as CO₂ sinks) and since 1990, the amount of carbon absorbed is larger than the amount released by deforestation.

Not all the CO₂ emitted to the atmosphere accumulates there.

Half of it is absorbed by sea and forests.

The real importance of each of the proposed causes can only be established through the exact quantification of every factor involved. Internal and external factors can be quantified by the analysis of climate simulations based on the best climate models.

The influence of external factors can be compared using the concept of radiative forcing. A positive radiative forcing warms the planet and negative radiative forcing cools the planet. Anthropogenic emissions of greenhouse gases, stratospheric ozone depletion, and solar radiation have positive radiative forcing and aerosols and land use have negative radiative forcing. (Source: IPCC)

Climate models

Climate simulations show that warming occurring from 1910 to 1945 can be explained by internal and natural forcing (variation in solar radiation) only, but warming occurring from 1976 to 2000 needs anthropogenic greenhouse gases emissions to be explained. The majority of the scientific community is now convinced that a significant proportion of observed global warming is caused by anthropogenic emissions of greenhouse gases. (Source: IPCC)

This conclusion depends on the accuracy of the models used and on the correct estimation of the external factors. The majority of scientists agrees that important climate features are incorrectly accounted by the climate models, but these scientists don't think that better models would change the conclusion. (Source: IPCC)

Critics point out that there are flaws in the models and external factors not taken into consideration that could change the conclusion above. The critics say that the climate simulations are unable to model the cooling effects of the particles, fitting the water vapor feedback and handling clouds. Critics also point out that the Sun may have a share of responsibility for the observed global warming greater than now thought by the majority of the scientific community. Some indirect solar effects may be very important and are not accounted by the models. So, the share of global warming caused by anthropogenic greenhouse gases may be lower than thought. (Source: The Skeptical Environmentalist)

Effects

Due to potential effects on human health, economy and the environment, global warming is the cause of great concern. Some important environmental changes have been observed and were linked to global warming. The examples of secondary evidence cited above (lessened snow cover, rising sea levels, weather changes) are examples of consequences of global warming that may influence not only human activities but also the ecosystems. Increasing global temperature means that ecosystems may change; some species may be forced out of their habitats (possibly to extinction) because of changing conditions while others may spread.

However, global warming can also have positive effects, since higher temperatures and higher CO₂ concentrations improve the ecosystems' productivity.

Satellite data shows that the productivity of the Northern Hemisphere increased since 1982. On the other hand, just the fact that the total amount of biomass produced increases is not necessarily all good, since biodiversity can still decrease even though a small number of species are flourishing.

Another cause of great concern is sea level rise. The sea levels are rising 0.01 to 0.02 meters per decade and some small countries in the Pacific Ocean are expressing concerns that if this rise in sea level doesn't stop, they soon will be entirely under water. Global warming causes the sea level to rise mainly because sea water expands, but some scientists are concerned that in the future, the polar ice caps and glaciers may melt. As a consequence, the sea level could rise several meters. At the moment, scientists are not expecting any major ice melting in the next 100 years. (Sources: IPCC for the data and The Mass Media for the general perception that climate change is important) Some researchers have found a negative correlation between sea level rise and average global temperature; water evaporates more quickly than it expands. (Source: SEPP)

As the climate gets hotter, evaporation will increase. This will cause heavier rainfall and more erosion. Many people think that it could result in more extreme weather as global warming progresses.

Global warming can also have other, less obvious effects. The North Atlantic drift, for instance, is driven by temperature changes. It seems as if it is diminishing as the climate grows warmer, and this means that areas like Scandinavia and Britain that are warmed by the drift might face a colder climate in spite of the general global warming.

The work of the Intergovernmental Panel on Climate Change (IPCC)

Since it is such an important issue, governments need predictions of future trends in global change so they can take political decisions to avoid undesired impacts. Global warming is being studied by the Intergovernmental Panel on Climate Change (IPCC). In its last report, IPCC made some predictions about future climate change. These predictions are the basis for current political and scientific discussion.

IPCC predictions are based on the same models used to establish the importance of the different factors in global warming. These models have the need for data of anthropogenic emissions of greenhouse gases and aerosols. This data is predicted from economical models based on 35 different scenarios. Scenarios go from pessimistic to optimistic and predictions of global warming depend on the kind of scenario considered. No scenario considers any kind of measures to avoid global warming.

In it's last report, IPCC stated that average surface temperature is projected to increase by 1.4 to 5.8 C over the period 1990 to 2100, and the sea level is projected to rise by 0.1 to 0.9 meters over the same period.

IPCC prediction are the best predictions available but are under strong scientific controversy. The IPCC recognizes that there is a need for better models and better scientific understanding of some climate phenomena, as well as the uncertainties involved. Critics point out that the available data is not sufficient to determine the real importance of greenhouse gases in climate change. Sensibility of climate to greenhouse gases may be overestimated because of some flaws in the models and because the importance of some external factors may be underestimated.

On the other hand, predictions are based on scenarios and the IPCC did not assign any probability to the 35 scenarios used. Critics point out that some of the scenarios that predict the largest impacts are not realistic because they contradict basic economical reasoning.

The United Nations Framework Convention on Climate Change and the Kyoto Protocol

Even if there are some doubts about its importance, global warming is perceived by the general public and by some political leaders as a potential threat. Reductions of the emissions of greenhouse gases was proposed. Being a tragedy of the commons-like problem, only an international agreement could reduce the emissions of greenhouse gases since voluntary reductions would be avoided by individual countries.

The United Nations Framework Convention on Climate Change (UNFCCC) establishes a process for developing an international response to the percieved global warming problem. Most of the countries in the world are parties to the UNFCCC, including all the major industrial nations. The UNFCCC, however, does not provide any binding emission targets.

Most of the parties to the UNFCCC, including all the major industrial nations, are party to the Kyoto Protocol to the UNFCCC, which provides binding greenhouse gas limits for developed countries (developing countries are not subject to limits under the Protocol). The limits are based on the level of their emissions in 1990; most developed countries are required to limit their emissions to a level below the 1990 level, although a few are permitted to limit their emissions to a level higher than what they emitted in 1990 (e.g. Iceland).

The United States, responsible for one-third of the emissions of greenhouse gases, has signed the Kyoto Protocol. However, the Bush Administration and the United States Senate have indicated that they do not intend to ratify it. This decision resulted in internal and international controversy with major political and ideological ramifications.

To evaluate the effectiveness of the Kyoto protocol, it is necessary to compare global warming with and without the agreement. Several independent authors agree that the impact of the Kyoto protocol in global warming is very small (a reduction of 0.15 in 2 C warming by 2100). Even some defenders of the Kyoto protocol agree that the impact of it is small, but they view it as a first step, with more political than practical importance, for future reductions. At the moment, an analysis made by the IPCC is needed to clarify this issue.

The Kyoto Protocol can also be evaluated by comparing costs and gains. Several economical analyses were made that show that the Kyoto Protocol is more expensive than the global warming that it avoids. Defenders of the Kyoto Protocol argue however that while the initial greenhouse gas cuts may have little effect, they set the political precedent for bigger (and more effective) cuts in the future.