Climate change may refer to a change in average weather conditions, or in the time variation of weather around longer-term average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change, often referred to as “global warming”.
Scientists actively work to understand past and future climate by using observations and theoretical models. A climate record — extending deep into the Earth’s past — has been assembled, and continues to be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record. General circulation models, based on the physical sciences, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.
Causes
On the broadest scale, the rate at which energy is received from the sun and the rate at which it is lost to space determine the equilibrium temperature and climate of Earth. This energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions.
Factors that can shape climate are called climate forcings or “forcing mechanisms”. These include processes such as variations in solar radiation, variations in the Earth’s orbit, variations in the albedo or reflectivity of the continents and oceans, mountain-building and continental drift and changes in greenhouse gas concentrations. There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings, while others respond more quickly. There are also key threshold factors which when exceeded can produce rapid change.
Forcing mechanisms can be either “internal” or “external”. Internal forcing mechanisms are natural processes within the climate system itself (e.g., the thermohaline circulation). External forcing mechanisms can be either natural (e.g., changes in solar output) or anthropogenic (e.g., increased emissions of greenhouse gases).
Whether the initial forcing mechanism is internal or external, the response of the climate system might be fast (e.g., a sudden cooling due to airborne volcanic ash reflecting sunlight), slow (e.g. thermal expansion of warming ocean water), or a combination (e.g., sudden loss of albedo in the arctic ocean as sea ice melts, followed by more gradual thermal expansion of the water). Therefore, the climate system can respond abruptly, but the full response to forcing mechanisms might not be fully developed for centuries or even longer.
Internal forcing mechanisms – Scientists generally define the five components of earth’s climate system to include atmosphere, hydrosphere, cryosphere, lithosphere (restricted to the surface soils, rocks, and sediments), and biosphere. Natural changes in the climate system (“internal forcings”) result in internal “climate variability”. Examples include the type and distribution of species, and changes in ocean currents.
- Ocean variability – The ocean is a fundamental part of the climate system, some changes in it occurring at longer timescales than in the atmosphere, massing hundreds of times more and having very high thermal inertia (such as the ocean depths still lagging today in temperature adjustment from the Little Ice Age).
- Life – Life affects climate through its role in the carbon and water cycles and such mechanisms as albedo, evapotranspiration, cloud formation, and weathering. Examples of how life may have affected past climate include: glaciation 2.3 billion years ago triggered by the evolution of oxygenic photosynthesis, glaciation 300 million years ago ushered in by long-term burial of decomposition-resistant detritus of vascular land plants (forming coal), termination of the Paleocene-Eocene Thermal Maximum 55 million years ago by flourishing marine phytoplankton, reversal of global warming 49 million years ago by 800,000 years of arctic azolla blooms, and global cooling over the past 40 million years driven by the expansion of grass-grazer ecosystems.
External forcing mechanisms
- 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, their correlation with the advance and retreat of the Sahara, and for their appearance in the stratigraphic record.
- Solar output – The Sun is the predominant source of energy input to the Earth. Both long- and short-term variations in solar intensity are known to affect global climate. Solar output also varies on shorter time scales, including the 11-year solar cycle and longer-term modulations.
- Volcanism – The eruptions considered to be large enough to affect the Earth’s climate on a scale of more than 1 year are the ones that inject over 0.1 Mt of SO2 into the stratosphere. This is due to the optical properties of SO2 and sulfate aerosols, which strongly absorb or scatter solar radiation, creating a global layer of sulfuric acid haze. On average, such eruptions occur several times per century, and cause cooling (by partially blocking the transmission of solar radiation to the Earth’s surface) for a period of a few years.
- Plate tectonics – Over the course of millions of years, the motion of tectonic plates reconfigures global land and ocean areas and generates topography. This can affect both global and local patterns of climate and atmosphere-ocean circulation. The position of the continents determines the geometry of the oceans and therefore influences patterns of ocean circulation. The locations of the seas are important in controlling the transfer of heat and moisture across the globe, and therefore, in determining global climate.
- Human influences – In the context of climate variation, anthropogenic factors are human activities which affect the climate. The scientific consensus on climate change is “that climate is changing and that these changes are in large part caused by human activities,” and it “is largely irreversible.” 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 the CO2 released by 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.
Non Renewable Energy and Climate Change
Non-renewable energy sources have fueled the world’s industrial complex for far too long, when analyzed in terms of sustainable development. It has reached a point where non renewable sources of energy are depleting at a rate faster than the growth rate of renewable substitutes .The costs of depleting non renewable energy sources are even more than the monetary benefits they provide to the economy. Unplanned exploitation of fossil fuels leads to environmental externalities like pollution. The massive adverse consequences of overexploitation of non-renewable sources are inexplicable and the trend has to be reversed soon before it is too late to do anything.
Carbon is a major source of fuel in non-renewable energy sources. When combustion takes place, carbon is mixed with oxygen and eventually forms carbon dioxide. It pollutes the environment and is one of the main factors responsible for global warming. In the last few years, the concentration of carbon dioxide has only increased in the atmosphere. Not to mention, climate change, acid rain and change in seasons are some of the other effects that have been observed by many people. In addition to these problems, scarce resources and rising prices imply that these resources cannot be used for lifetime. The need of the hour is to look for some alternative sources of energy and protect our environment from such harmful gases.
Renewable Energy And Climate Change
The causes and effects of climate change can be described with the help of the following diagram :
In a developing country like India, with the vast majority of her citizen’s below the poverty line and inefficient environmental protection programmes , the welfare of the nation is at stake if drastic steps to reverse the climate change phenomenon are not taken.
A comprehensive guide to using renewable energy to mitigate the ill effects of climate change was published on May 9,2011 by “The United Nations Intergovernmental Panel on climate change”. It was a special report titled “Renewable energy sources and climate change mitigation” and was developed under the leadership of Ottmar Edenhofer.
Renewable energy can contribute to “social and economic development, energy access, secure energy supply, climate change mitigation, and the reduction of negative environmental and health impacts”. In the report, the IPCC said “as infrastructure and energy systems develop, in spite of the complexities, there are few, if any, fundamental technological limits to integrating a portfolio of renewable energy technologies to meet a majority share of total energy demand in locations where suitable renewable resources exist or can be supplied”. Under favourable circumstances, cost savings in comparison to non-renewable energy use exist.
IPCC scenarios “generally indicate that growth in renewable energy will be widespread around the world”. The IPCC said that if governments were supportive, and the full range of renewable technologies were deployed, renewable energy could account for almost 80% of the world’s energy supply within four decades. Rajendra Pachauri, chairman of the IPCC, said the necessary investment in renewables would cost only about 1% of global GDP annually. This approach could keep greenhouse gas concentrations to less than 450 parts per million, the safe level beyond which climate change becomes catastrophic and irreversible.
Sensitivity, Adaptibility and Vulnerability
The potential impacts of climate change on the environment and socio-economic systems can be understood in terms of sensitivity, adaptability and vulnerability of the system.
Both the magnitude and the rate of climate change are important in determining the sensitivity, adaptability and vulnerability of a system.
