Climate change is a change in the statistical distribution of weather patterns when that change lasts for an expanded time period i.E., decades to millions of years . weather 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 . weather change is instigated by factors like biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic eruptions. Certain human actions have also been identified as important causes of recent weather change, frequently called world warming.
Scientists actively work to understand past and future weather by using observations and theoretical models. A weather recordextending deep into the Earth's pasthas been assembled, and continues to be built up, depending 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 offered
by the instrumental record. General circulation models, depending on the physical sciences, are frequently used in theoretical approaches to go with past weather data, make future projections, and link causes and effects in weather change.
On the broadest scale, the rate at which energy is received from the Sun and the rate at which it's lost to space find out the equilibrium temperature and weather of Earth. This energy is circulated around the globe by winds, ocean currents, and other mechanisms to influence the climates of different regions.
Factors that can form weather are called weather forcings or "forcing mechanisms".7 these are processes like 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 range of weather change feedbacks that can either amplify or diminish the initial forcing. Some parts of the weather system, like the oceans and ice caps, react more gradually in reaction to weather forcings, while others react more quickly. There are key threshold factors which when exceeded can create fast change.
Forcing mechanisms may be either "internal" or "external". interior forcing mechanisms are natural processes inside the weather system itself e.G., the thermohaline circulation . External forcing mechanisms may be either natural e.G., changes in solar output or anthropogenic e.G., increased emissions of greenhouse gases .
if the initial forcing system is interior or external, the answer of the weather system may be fast e.G., a sudden cooling caused by airborne volcanic ash reflecting sunlight, slow e.G. Thermal expansion of warming ocean water, or a mix e.G., sudden loss of albedo in the arctic ocean as sea ice melts, followed by more steady thermal expansion of the water . so, the weather system can react abruptly, but the full answer to forcing mechanisms may not be completely worked on for centuries or longer.
The Sun is the main supply of energy input to the Earth. Other resources include geothermal energy from the Earth's core, and heat from the decay of radioactive compounds. Both long and short term variations in solar intensity are recognized to influence world weather.
Three to four billion years ago, the Sun emitted only 70 as much power as it does today. If the atmospheric structure had been the same as today, liquid water shouldn't existed on Earth. but, there's evidence for the presence of water on the early Earth, in the Hadean and Archean eons, leading to what is called the faint young Sun paradox. Hypothesized solutions to this paradox include a very different atmosphere, with much higher concentrations of greenhouse gases than now exist. Over the following roughly four billion years, the energy output of the Sun increased and atmospheric structure changed. The Great Oxygenation Event oxygenation of the atmosphere around 2.4 billion years ago was the most notable alteration. Over the next five billion years, the Sun's final death as it becomes a red giant, then a white dwarf will have big effects on weather, with the red giant phase possibly ending any life on Earth that survives till that time.
Solar output also differs on shorter time scales, as well as the 11-year solar cycle and longer term modulations. Solar intensity variations possibly consequently of the Wolf, Sprer and Maunder Minimum are considered to have been powerful in triggering the Little Ice Age,42 and some of the warming observed from 1900 to 1950. The cyclical nature of the Sun's energy output isn't still completely understood, it differs from the slow change that's happening inside the Sun as it ages and evolves. Research indicates that solar variability has had effects as well as the Maunder minimum from 1645 to 1715 A.D., part of the Little Ice Age from 1550 to 1850 A.D. That has been marked by relative cooling and greater glacier extent than the centuries before and then. Some studies point toward solar radiation increases from cyclical sunspot activity influencing world warming, and weather can be influenced by the sum of all effects solar variation, anthropogenic radiative forcings, etc. .
The eruptions considered to be big enough to influence the Earth's weather on a scale of more than one year are the ones that inject over 100,000 tons of SO2 into the stratosphere.49 This is caused by the optical properties of SO2 and sulfate aerosols, which strongly take in or scatter solar radiation, creating a world level of sulfuric acid haze. On average, such eruptions happen some number of times per century, and because cooling by partially blocking the transmission of solar radiation to the Earth's surface for a period of some years.
The eruption of Mount Pinatubo in 1991, the second biggest terrestrial eruption of the 20th century, influenced the weather considerably, subsequently world temperatures decreased by about 0.5 C 0.9 F for up to three years.5152, the cooling over big parts of the Earth reduced surface temperatures in 1991-93, the equivalent to a reduction in net radiation of four watts per square meter. The Mount Tambora eruption in 1815 caused the Year Without a Summer.54 Much bigger eruptions, called big igneous provinces, happen only some times every fifty hundred million years through flood basalt, and caused in Earth past world warming and mass extinctions.
Small eruptions, with injections of less than 0.1 Mt of sulfur dioxide into the stratosphere, affect the atmosphere only subtly, as temperature changes are comparable with natural variability. but, because smaller eruptions happen at a much higher frequency, they too have a important affect on Earth's atmosphere.
Seismic monitoring maps current and future trends in volcanic actions, and tries to develop early warning systems. In weather modelling the aim is to study the physical mechanisms and feedbacks of volcanic forcing.