INTRODUCTION: Climatic change is nothing but the change in the average weather or a change in the distribution of weather events around the earth. It's more qualified as anthropogenic climate change, more generally known as global warming.
CAUSES OF CLIMATIC CHANGE: Factors that can shape climate are climate forcing. These include such processes as variations in solar radiation, deviations in the Earth's orbit, mountain-building and continental drift, and changes in green house gas concentrations. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcing because of their large mass. Therefore, the climate system can take centuries or longer to fully respond to new external forcing.
Main Reasons:Increased warming:• The problem that we face today is that the ‘blanket’ of greenhouse gases that occurs naturally in the troposphere is quickly getting thicker and this results in the rapid warming of the world’s climate.
• The temperature rises when the climate system adjusts to restore the balance between incoming and outgoing energy. A rise in temperature, global warming, occurs in addition to other changes in cloud cover and wind patterns.
• Up until now the earth’s average temperature has been stable but now the ‘blanket’ which regulates the planet’s climate is getting thicker at an unprecedented speed due to the large amount of artificial emissions of greenhouse gases.These emissions result in an enchanced greenhouse effect.
IMPORTANT EFFECT : Over the past 100 years (1906-2005), the Earth’s average surface temperature has risen by around 0.74°C. The rate of warming averaged over the last 50 years is nearly twice the rate for the last 100 years.
Emission of Carbon dioxide ( CO2) in the atmosphere: The artificial greenhouse gases that are causing global warming largely come from fossil fuels formed by long-dead plants and animals and from the oceans due to the increase in the Earth's temperature.
Other sources caused by humanity are burning coal, oil and natural gas releases.Long-lived gases such as CFCs, HFCs and PFCs, used in air conditioning and refrigeration, are manufactured by industry and eventually enter the atmosphere.
Almost everything we produce and consume today means GHG emissions. Many of these GHG-emitting activities are now essential to the global economy and form a fundamental part of modern life.
Getting from one place to another, transport, demands a lot of energy as well. Energy which results in GHG emissions and housing accounts for 30 percent of global GHG emissions.
Solar output Variations in solar activity during the last several centuries based on observations of sunspots and beryllium isotopes.
The sun is the predominant source for energy input to the Earth. Both long- and short-term variations in solar intensity are known to affect global climate.
Early in Earth's history the sun emitted only 70% as much power as it does today. With the same atmospheric composition as exists today, liquid water should not have existed on Earth. However, there is evidence for the presence of water on the early Earth, in the Hadean and Archean eons, leading to what is known as the faint young sun paradox. Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist .Over the following approximately 4 billion years, the energy output of the sun increased and atmospheric composition changed, with the oxygenation of the atmosphere being the most notable alteration. The changes in luminosity, and the sun's ultimate death as it becomes a red giant and then a white dwarf, will have large effects on climate, with the red giant phase possibly ending life on Earth.
Solar output also varies on shorter time scales, including the 11-year solar cycle and longer-term modulations. The 11-year sunspot cycle produces low-latitude warming and high-latitude cooling over limited areas of statistical significance in the stratosphere with an amplitude of approximately 1.5°C.
But although "variability associated with the 11-yr solar cycle has a significant influence on stratospheric temperatures, there is still no consensus on the exact magnitude and spatial structure".These stratospheric variations are consistent with the idea that excess equatorial heating can drive thermal winds. In the near-surface troposphere, there is only a small change in temperature (on the order of a tenth of a degree, and only statistically significant in limited areas underneath the peaks in stratospheric zonal wind speed) due to the 11-year solar cycle. The cyclical nature of the sun's energy output is not yet fully understood; it differs from the very slow change that is happening within the sun as it ages and evolves, with some studies pointing toward solar radiation increases from cyclical sunspot activity affecting global warming.
Orbital variations Slight variations in Earth's orbit lead to changes in the seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe. There is very little change to the area-averaged annually-averaged sunshine; but there can be strong changes in the geographical and seasonal distribution.
The three types of orbital variations are variations in
• Earth's eccentricity,
• changes in the tilt angle of Earth's axis of rotation, and
• Precession of Earth's axis.
Combined together, these produce Milankovitch cycles which have a large impact on climate and are notable for their correlation to glacial and interglacial periods.
VolcanismVolcanism is a process of conveying material from the crust and mantle of the Earth to its surface.
Volcanic eruptions, geysers, and hot springs, are examples of volcanic processes which release gases and/or particulates into the atmosphere.
Eruptions cause cooling (by partially blocking the transmission of solar radiation to the Earth's surface) for a period of a few years. The eruption of Mount Pinatubo in 1991, the second largest terrestrial eruption of the 20th century (after the 1912 eruption of Novarupta) affected the climate substantially. Global temperatures decreased by about 0.5 °C (0.9 °F). The eruption of Mount Tambora in 1815 caused the Year Without a Summer. Much larger eruptions, known as large igneous provinces, occur only a few times every hundred million years, but may cause global warming and mass extinctions.
Volcanoes are also part of the extended carbon cycle. Over very long (geological) time periods, they release carbon dioxide from the Earth's crust and mantle, counteracting the uptake by sedimentary rocks and other geological carbon dioxide sinks. According to the US Geological Survey, however, estimates are that human activities generate more than 130 times the amount of carbon dioxide emitted by volcanoes.
Ocean variabilityThe ocean is a fundamental part of the climate system. Short-term fluctuations (years to a few decades) such as
• the El Niño–Southern Oscillation,
• the Pacific decadal oscillation,
• the North Atlantic oscillation, and
• the Arctic oscillation, represent climate variability rather than climate change.
On longer time scales, alterations to ocean processes such as thermohaline circulation play a key role in
redistributing heat by carrying out a very slow and extremely deep movement of water, and the long-term redistribution of heat in the world's oceans.
Human influences The chain of causality of human influence on the climate is direct and unambiguous (for example, the effects of irrigation on local humidity), whilst in other instances it is less clear. Presently the scientific consensus on climate change is that human activity is very likely the cause for the rapid increase in global average temperatures over the past several decades.[Consequently, the debate has largely shifted onto ways to reduce further human impact and to find ways to adapt to change that has already occurred.
Of most concern in these anthropogenic factors is the increase in CO2 levels due to emissions from fossil fuel combustion, followed by aerosols (particulate matter in the atmosphere) and cement manufacture. Other factors, including land use, ozone depletion, animal agriculture and deforestation, are also of concern in the roles they play - both separately and in conjunction with other factors - in affecting climate, microclimate, and measures of climate variables.
Physical evidence for climatic change Some can think of having evidence for this climatic change, and my answer to those pessimists is optimistic. Here in this section we are going to discuss about the various factors which forms the evidence.
Historical & Archaeological evidence
Glaciers
Vegetation
Ice cores
Pollen analysis
Insects
Sea level change
Historical & Archaeological evidence : Climate change in the recent past may be detected by corresponding changes in settlement and agricultural patterns. Archaeological evidence, oral history and historical documents can offer insights into past changes in the climate. Climate change effects have been linked to the collapse of various civilisations.
Glaciers
Glaciers are among the most sensitive indicators of climate change,[30] advancing when climate cools (for example, during the period known as the Little Ice Age) and retreating when climate warms. Glaciers grow and shrink, both contributing to natural variability and amplifying externally forced changes
Vegetation
A change in the type, distribution and coverage of vegetation may occur given a change in the climate; this much is obvious. In any given scenario, a mild change in climate may result in increased precipitation and warmth, resulting in improved plant growth and the subsequent sequestration of airborne CO2. Larger, faster or more radical changes, however, may well result in vegetation stress, rapid plant loss and desertification in certain circumstances.
Ice Cores
Analysis of ice in a core drilled from a ice sheet such as the Antarctic ice sheet, can be used to show a link between temperature and global sea level variations. The air trapped in bubbles in the ice can also reveal the CO2 variations of the atmosphere from the distant past, well before modern environmental influences. The study of these ice cores has been a significant indicator of the changes in CO2 over many millennia, and continue to provide valuable information about the differences between ancient and modern atmospheric conditions.
Pollen Analysis :
Palynology is the study of contemporary and fossil palynomorphs, including pollen. Palynology is used to infer the geographical distribution of plant species, which vary under different climate conditions. Different groups of plants have pollen with distinctive shapes and surface textures, and since the outer surface of pollen is composed of a very resilient material, they resist decay. Changes in the type of pollen found in different sedimentation levels in lakes, bogs or river deltas indicate changes in plant communities; which are dependent on climate conditions.
Insects
Remains of beetles are common in freshwater and land sediments. Different species of beetles tend to be found under different climatic conditions. Given the extensive lineage of beetles whose genetic makeup has not altered significantly over the millennia, knowledge of the present climatic range of the different species, and the age of the sediments in which remains are found, past climatic conditions may be inferred.
Sea level change
Global sea level change for much of the last century has generally been estimated using tide gauge measurements collated over long periods of time to give a long-term average. More recently, altimeter measurements — in combination with accurately determined satellite orbits — have provided an improved measurement of global sea level change.
COPENHAGEN DEAL
So what’s the deal?
The Copenhagen Accord, as it was named last night, makes reference to the need to keep temperature rises to no more than 2°C and says rich countries will commit to cutting greenhouse gases and developing nations will take steps to limit the growth of their emissions – but sets no targets.
Under the accord, countries will set out their pledges for the action they plan to take to tackle climate change, in an appendix to the document, and will provide information to other nations on their progress.
There are promises of short term finance to the tune of $10bn a year over three years for poor countries to help them fight climate change, and a long term funding package worth $100bn a year by 2020.
There are also references to the importance of reducing deforestation and efforts to give poor countries access to technology that helps them go green.
Is it what we expected?
Originally, the plan was for the Copenhagen talks to deliver a comprehensive, legally-binding international deal to tackle climate change. But it has been clear for some time that such an agreement would not materialise at these talks.
In the immediate run-up to the negotiations, it was hoped a political agreement could be reached, which could then be turned into a legal treaty next year.
We did come out of the talks with a political agreement drawn up by leaders and which was eventually accepted by the conference of more than 190 countries this morning, but there are some major holes in the deal.
So what's missing?
Some key things. Firstly there is no mention of any long term global emissions cut targets – although the 50% reduction by 2050, which was dropped at the last minute, is what would be needed to meet the 2°C temperature cap still referred to in the deal. There is no target, either, for the long term cuts developed countries must make.
Perhaps more significant, though, is the absence of any timescale for when or even if the deal could be turned into a legally-binding treaty.
And a series of other agreements which would have formed part of the deal, such as one on how to tackle deforestation, have been shelved until the next conference.
Who drew it up?
Leaders had expected to arrive in Copenhagen for the end of the talks to sign an agreement drawn up by negotiators, but when they arrived – mostly on Thursday – officials had not managed to agree something they could give them.
As a result heads of state and government from a number of countries themselves ended up thrashing out parts of the text in the early hours of Friday morning, and held talks with one another while officials and negotiators continued to work out details throughout the day.
Eventually the US announced it had secured agreement with China, India, Brazil and South Africa for the deal, which got the eventual backing of the EU and – in the end – the majority of developed and developing countries at the conference.
This was billed as a historic opportunity for the world to tackle climate change, but faces have been glum around the talks in the wake of the announcement.
Conclusion:
Thus we have studied various issues related to CLIMATE CHANGE including the source, preventive measures and copenhagen deal. From this , it is evident that only climate and change are the two things which always are subjected to change.
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