Impact of Climate Change and Indicators of Climate Change
Climate change is the subject of how weather patterns change over decades or longer. Climate change takes place due to natural and human influences.
Since the Industrial Revolution (i.e., 1750), humans have contributed to climate change through the emissions of GHGs and aerosols, and through changes in land use, resulting in a rise in global temperatures.
Evidence for a warming world comes from multiple independent climate indicators, from high up in the atmosphere to the depths of the oceans.
They include changes in surface, atmospheric and oceanic temperatures; glaciers; snow cover; sea ice; sea level and atmospheric water vapour. Scientists from all over the world have independently verified this evidence many times. That the world has warmed since the 19th century is unequivocal.
This unit also elaborates on the impact of global warming and climate change, and also proffers solution to the menace of global warming.
1. Sun’s Output
Change in the amount of energy emitted by the Sun is a prime candidate as a cause of climate variability. And there is no doubt that on the longest timescales of Earth’s geological history, trends in solar output have played a major role in shaping the Earth’s climate and will continue to do so in the future.
Within our lifetime, though, of more concern are variations on the 10- to 100-year timescales. It has been known for many centuries that the face of the sun exhibits dark patches, sunspots, and that the number of sunspots varies with a fairly regular cycle of around 11 years.
Is this sunspot cycle an indicator of processes within the sun that might also affect the solar output and, hence, Earth’s climate? Despite many studies, the evidence is still controversial.
Sunspot cycles have been found in climate parameters, but the fluctuations are weak and tend to appear and disappear without reason.
The 11-year sunspot cycle itself varies in strength on timescale of 80 years and longer, and these longer- term fluctuations have also been linked to climatic change. In the early 1600s, the sunspot cycle almost disappeared and this phenomenon, the so-called Maunder Minimum, has been associated with the height of the Little Ice Age.
It has also been claimed that the warming of the 20th century was largely due to trends in sunspot activity, for example, in the length of the sunspot cycle. But, again, the evidence for these apparent correlations is not strong.
Moreover, the fluctuations in solar output that likely accompanied these sunspot trends were not really sufficient to generate the observed climate changes, without some amplifying mechanism.
2. Milankovitch Cycles
On time scales of a thousand years and longer, changes in the character of the Earth‘s orbit around the Sun and in its rotation can significantly affect the way in which the energy from the Sun is distributed by season and by latitude. This is known as the Milankovitch Effect, and it generates changes which are cyclic in nature.
Comparison of the changes predicted by astronomical calculations with the observed climate record suggests that this mechanism has played a part in inducing the shift from ice age to interglacial conditions on time scales of 10,000 to 100,000 years. But in order to explain the scale of the observed variations, it is necessary to invoke other factors.
One possibility is that the basic effect is magnified by the release and uptake of carbon dioxide as climate alters.
3. Volcanic Eruption
Explosive volcanic eruptions can inject large quantities of dust and the gas, sulphur dioxide, high into the atmosphere. Whereas volcanic debris in the lower atmosphere falls out or is rained out within days, the veil of pollution in the upper atmosphere is above the weather and may remain for several years, gradually spreading to cover much of the globe.
The volcanic pollution results in a substantial reduction in the stream of solar energy as it passes through the upper layers of the atmosphere, reflecting a significant amount back out to space.
Observational and modeling studies of the likely effect of recent volcanic eruptions suggest that an individual eruption may generate global cooling amounting to two or three tenths of a degree Celsius.
The effect lasts for a year or two. Major eruptions have not been common this century, occurring once every ten to twenty years, so the long-term influence has been slight. The influence on climate has been on the year- to-year time scale.
Other forms of pollution can affect the passage of heat and light through the air dust thrown up by windstorms or human activity, for example but the most significant factor at this time is believed to be the rising amount of greenhouse gases, such as carbon dioxide and methane, in the atmosphere.
Indicators of Climate Change
1. Rise in Global Temperature
Evidence for a warming world comes from multiple independent climate indicators, from high up in the atmosphere to the depths of the oceans.
They include changes in surface, atmospheric and oceanic temperatures; glaciers; snow cover; sea ice; sea level and atmospheric water vapour. Scientists from all over the world have independently verified this evidence many times. That the world has warmed since the 19th century is unequivocal.
Discussion about climate warming often centres on potential residual biases in temperature records from land based weather stations. These records are very important, but they only represent one indicator of changes in the climate system.
Broader evidence for a warming world comes from a wide range of independent physically consistent measurements of many other, strongly interlinked, elements of the climate system.
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A rise in global average surface temperatures is the best-known indicator of climate change. Although each year and even decade is not always warmer than the last, global surface temperatures have warmed substantially since 1900.
Warming land temperatures correspond closely with the observed warming trend over the oceans. Warming oceanic air temperatures, measured from aboard ships, and temperatures of the sea surface itself also coincide, as borne out by many independent analyses.
The atmosphere and ocean are both fluid bodies, so warming at the surface should also be seen in the lower atmosphere, and deeper down into the upper oceans, and observations confirm that this is indeed the case.
Analyses of measurements made by weather balloon radiosondes and satellites consistently show warming of the troposphere, the active weather layer of the atmosphere.
More than 90% of the excess energy absorbed by the climate system since at least the 1970s has been stored in the oceans as can be seen from global records of ocean heat content going back to the 1950s.
As the oceans warm, the water itself expands. This expansion is one of the main drivers of the independently observed rise in sea levels over the past century. Melting of glaciers and ice sheets also contribute, as do changes in storage and usage of water on land.
A warmer world is also a moister one, because warmer air can hold more water vapour. Global analyses show that specific humidity, which measures the amount of water vapour in the atmosphere, has increased over both the land and the oceans.
The frozen parts of the planet known collectively as the cryosphere, affects, and are affected by, local changes in temperature.
The amount of ice contained in glaciers globally has been declining every year for more than 20 years, and the lost mass contributes, in part, to the observed rise in sea level.
2. Changes in Snow Temperature
Snow cover is sensitive to changes in temperature, particularly during the spring, when snow starts to melt. Spring snow cover has shrunk across the NH since the 1950s.
Substantial losses in Arctic sea ice have been observed since satellite records began, particularly at the time of the minimum extent, which occurs in September at the end of the annual melt season.
By contrast, the increase in Antarctic sea ice has been smaller. Individually, any single analysis might be unconvincing, but analysis of these different indicators and independent data sets has led many independent research groups to all reach the same conclusion.
From the deep oceans to the top of the troposphere, the evidence of warmer air and oceans, of melting ice and rising seas all points unequivocally to one thing: the world has warmed since the late 19th century.
Effects on hydrological systems;
Changes on terrestrial biological systems;
Trend towards earlier greening of vegetation and longer thermal growing season;
Changes in marine and freshwater biological systems associated with rising water temperatures, as well as related changes in ice cover, salinity, oxygen levels and circulation;
Ocean acidification with an average decrease in pH of 0.1 units. The associated effects on the marine biosphere were not documented at the time of the assessment.
In summary, as the oceans warm, the water itself expands. This expansion is one of the main drivers of the independently observed rise in sea levels over the past century. Melting of glaciers and ice sheets also contribute, as do changes in storage and usage of water on land.
A warmer world is also a moister one, because warmer air can hold more water vapour. Global analyses show that specific humidity, which measures the amount of water vapour in the atmosphere, has increased over both the land and the oceans.
Discussion about climate warming often centres on potential residual biases in temperature records from land based weather stations. These records are very important, but they only represent one indicator of changes in the climate system.
Broader evidence for a warming world comes from a wide range of independent physically consistent measurements of many other, strongly interlinked, elements of the climate system.
Despite many studies, the evidence is still controversial. Sunspot cycles have been found in climate parameters, but the fluctuations are weak and tend to appear and disappear without reason.
The 11-year sunspot cycle itself varies in strength on timescale of 80 years and longer, and these longer-term fluctuations have also been linked to climatic change. In the early 1600s, the sunspot cycle almost disappeared and this phenomenon, the so-called Maunder Minimum, has been associated with the height of the Little Ice Age.
It has also been claimed that the warming of the 20th century was largely due to trends in sunspot activity.Change in the amount of energy emitted by the Sun is a prime candidate as a cause of climate variability. And there is no doubt that on the longest timescales of Earth’s geological history, trends in solar output have played a major role in shaping the Earth’s climate and will continue to do so in the future.
Evidence for a warming world comes from multiple independent climate indicators, from high up in the atmosphere to the depths of the oceans.
They include changes in surface, atmospheric and oceanic temperatures; glaciers; snow cover; sea ice; sea level and atmospheric water vapour. Scientists from all over the world have independently verified this evidence many times.
That the world has warmed since the 19th century is unequivocal. Discussion about climate warming often centres on potential residual biases in temperature records from land based weather stations.
A rise in global average surface temperatures is the best-known indicator of climate change. Although each year and even decade is not always warmer than the last, global surface temperatures have warmed substantially since 1900. Warming land temperatures correspond closely with the observed warming trend over the oceans.
Change in the amount of energy emitted by the Sun, Milankovitch Effect, volcanic eruptions and other forms of pollutions which injects gases into the atmosphere have variable effects on climate change.
Evidence for a warming world comes from multiple independent climate indicators, from high up in the atmosphere to the depths of the oceans. They include changes in surface, atmospheric and oceanic temperatures; glaciers; snow cover; sea ice; sea level and atmospheric water vapour.
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