Global Warming Is the Increase of Earth’s average surface temperature due to effect of greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from deforestation, which trap heat that would otherwise escape from Earth. Earth’s climate Is mostly Influenced by the first 6 miles or so of the atmosphere which contains most of the matter making up the atmosphere. This is really a very thin layer if you think about it.
In the book The End of Nature, author Bill Mimicking tells of walking three miles to from his cabin in the Adirondacks to buy food. Afterwards, he realized that on this short journey he had traveled a distance equal to that of the layer of the atmosphere where almost all the action of our climate is contained. In fact, if you were to view Earth from space, the principle part of the atmosphere would only be about as thick as the skin on an onion! Realizing this makes it more plausible to suppose that human beings can change the climate.
A look at the amount of greenhouse gases we are spewing into the atmosphere (see below), makes It even more plausible. One of the most vigorously debated topics on Earth Is the Issue of limited change, and the National Environmental Satellite, Data, and Information Service (NESSES) data centers are central to answering some of the most pressing global change questions that remain unresolved. The National Climatic Data Center contains the instrumental and pale climatic records that can precisely define the nature of climatic fluctuations at time scales of a century and longer.
Among the diverse kinds of data platforms whose data contribute to Nonce’s resources are: Ships, buoys, weather stations, weather balloons, satellites, radar and many climate proxy records such as tree rings and ice cores. The National Oceanographic Data Center contains the subsurface ocean data which reveal the ways that heat is distributed and redistributed over the planet. Knowing how these systems are changing and how they have changed In the past Is crucial to understanding how they will change In the future.
And, for climate Information that extends from hundreds to thousands of years, pale climatology data, also available from the National Climatic Data Center, helps to provide longer term perspectives. Internationally, the Intergovernmental Panel on Climate Change (EPIC), under the auspices of the united Nations (UN), World Meteorological Organization (WHOM), and the United Nations Environment Program (UNEVEN), is the most senior and authoritative body providing scientific advice to global policy makers. The EPIC met in full session in 1990, 1995, 2001 and in 2007.
They address issues such as the buildup of greenhouse gases, evidence, attribution, and prediction of climate change, impacts of climate change, and policy options. Listed below are a number of questions commonly addressed to climate scientists, and brief replies (based on EPIC reports and other research) In common, understandable language. This list will be periodically updated, as new scientific evidence comes to light. Global warming Is the continuing rise In the average temperature of Earth’s atmosphere and oceans.
The evidence for this temperature rise is unequivocal and, with greater than 90% that increase concentrations of greenhouse gases in the atmosphere, such as and burning of fossil fuels. This finding is recognized by the national science academies of all the major industrialized countries. The instrumental temperature record shows that the average global surface temperature increased by 0. 74 co (1. 3 OF) during the 20th century. Climate model projections are summarized in the 2007 Fourth Assessment Report (ARE) by the Intergovernmental Panel on Climate Change (EPIC).
They indicate that during the 21st century the global surface temperature is likely to rise a further 1. 5 to 1. 9 co (2. 7 to 3. 4 OF) for their lowest emissions scenario and 3. 4 to 6. 1 co (6. 1 to 11 OF) for their highest. The ranges of these estimates arise from the use of models with differing sensitivity to greenhouse gas concentrations. An increase in global temperature will cause sea levels to rise and will change the mount and pattern of precipitation, and a probable expansion of subtropical deserts.
Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent occurrence of extreme weather events including headwater, droughts and heavy rainfall events, species extinctions due to shifting temperature regimes, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional changes is uncertain.
In a 4 co world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon which human livelihoods depend would not be preserved. Global Warming and Population: It seems there has been a recent interest in associating climate change/global warming with “over population” and that countries such as China and India have to do more to help contain global warming. Yet rich countries have a lot to do themselves.
There were agreed reasons why developing countries were exempt from initial greenhouse gas emission targets: it was the emissions from rich countries that accumulated in the atmosphere for so long to trigger climate change. Climate Change: Global surface temperatures have increased about 0. ICC (plus or minus 0. ICC) since the late-19th century, and the linear trend for the past 50 years of 0. ICC (plus or minus 0. ICC) per decade is nearly twice that for the past 100 years. The warming has not been globally uniform.
Some areas (including parts of the southeastern U. S. And parts of the North Atlantic) have, in fact, cooled slightly over the last century. The cent warmth has been greatest over North America and Eurasia between 40 and INN. Lastly, seven of the eight warmest years on record have occurred since 2001 temperature trends in the lower and mid- troposphere (between about 2,500 and 26,000 Ft. ) using both satellite and radiations (weather balloon) data show warming rates that are similar to those observed for surface air temperatures.
These warming rates are consistent with their uncertainties and these analyses reconcile a discrepancy between warming rates noted on the EPIC Third Assessment Report (U. S. Climate Change Science Plan Synthesis and Assessment Report 1 . ). An enhanced greenhouse effect is expected to cause cooling in higher parts of the atmosphere because the increased “blanketing” effect in the lower atmosphere holds in more heat, allowing less to reach the upper atmosphere. Cooling of the lower stratosphere (about 49,000-79,500 Ft. Since 1979 is shown by both satellite Microwave Sounding Unit and radiations data (see previous figure), but is larger in the radiations data likely due to uncorrected errors in the radiations data. Relatively cool surface and troposphere temperatures, and a relatively warmer lower stratosphere, were observed in 1992 and 1993, following the 1991 eruption of Met. Punctuation. The warming reappeared in 1994. A dramatic global warming, at least partly associated with the record El Onion, took place in 1998.
This warming episode is reflected from the surface to the top of the troposphere. There has been a general, but not global, tendency toward reduced diurnal temperature range (DIR: the difference between daily high or maximum and daily low or minimum temperatures) over about 70% of the global land mass since the middle of the 20th century. However, for the period 1979-2005 the DIR shows no trend since the trend in both maximum and minimum enraptures for the same period are virtually identical; both showing a strong warming signal.
A variety of factors likely contribute to this change in DIR, particularly on a regional and local basis, including changes in cloud cover, atmospheric water vapor, land use and urban effects. Indirect indicators of warming such as borehole temperatures, snow cover, and glacier recession data, are in substantial agreement with the more direct indicators of recent warmth. Evidence such as changes in glacial mass balance (the amount of snow and ice contained in a glacier) is useful since it not only provides qualitative support for existing dermatological data, but glaciers often exist in places too remote to support meteorological stations.
The records of glacial advance and retreat often extend back further than weather station records, and glaciers are usually at much higher altitudes than weather stations, allowing scientists more insight into temperature changes higher in the atmosphere. Climate Conference: The Conference of Parties Ill (COOP), Kyoto, Japan, the Kyoto conference on climate change took place. There, developed countries agreed to specific targets for cutting their emissions of greenhouse gases. A general framework was defined for this, with Protocol.
The US proposed to Just stabilize emissions and not cut them at all, while the European Union called for a 15% cut. In the end, there was a trade off, and industrialized countries were committed to an overall reduction of emissions of greenhouse gases to 5. 2% below 1990 levels for the period 2008 – 2012. (The Intergovernmental Panel on Climate Change said in its 1990 report that a 60% reduction in emissions was needed… ) As with the following COP meetings, there was enormous media propaganda by affected big businesses and by countries such as the U. S. Who were openly hostile to the treaty.
In fact one of the first things George Bush did when he came to power was to oppose the Kyoto Protocol. Ozone Layer and Climate Change: Scientists believe that Global Warming will lead to a weaker Ozone layer, because as the surface temperature rises, the stratosphere (the Ozone layer being found in the upper part) will get colder, making the natural repairing of the Ozone slower. Related Global Warming: Related Global Warming are not caused by global warming. Clear evidence exists from a variety of sources (including archaeological studies) that El Ions have been resent for thousands, and some indicators suggest maybe millions, of years.
However, it has been hypothesized that warmer global sea surface temperatures can enhance the, and it is also true that El Ions have been more frequent and intense in recent decades. Hydrological Cycle Changing: Globally-averaged land-based precipitation shows a statistically insignificant upward trend with most of the increase occurring in the first half of the 20th century. Further, precipitation changes have been spatially variable over the last century. On a regional basis increases in annual precipitation have occurred in the higher latitudes f the Northern Hemisphere and southern South America and northern Australia.
Decreases have occurred in the tropical region of Africa, and southern Asia. Due to the difficulty in measuring precipitation, it has been important to constrain these observations by analyzing other related variables. The measured changes in precipitation are consistent with observed changes in stream flow, lake levels, and soil moisture (where data are available and have been analyzed). Northern Hemisphere snow cover extent has consistently remained below average since 1987, and has decreased by about 10% since 1966.
This is mostly due to a decrease in spring and summer snow extent over both the Eurasian and North American continents since the mid-sass. Winter and autumn snow cover extent have shown no significant trend for the northern hemisphere over the same period. Clouds are also an important indicator of climate change. Surface-based observations of cloud cover suggest increases in total cloud cover over many continental regions. This increase since 1950 is consistent with regional increases in precipitation for the same period. However, global analyses of cloud cover over land for the 1976-2003 period show little change.
Atmosphere Ocean Changing: A rather abrupt change in the El Onion – Southern Oscillation behavior occurred around 1976/77. Often called the climatic shift of 1976/77, this new regime has persisted. There have been relatively more frequent and persistent El Onion episodes years (the period of instrumental record). Changes in precipitation over the tropical Pacific are related to this change in the El Onion – Southern Oscillation, which has also affected the pattern and magnitude of surface temperatures. However, it is unclear as to whether this apparent change in the ONES cycle is related to global warming.
Climate Become more Variable or Extent: Examination of changes in climate extremes requires long-term daily or even hourly data sets which until recently have been scarce for many parts of the globe. However these data sets have become more widely available allowing research into changes in temperature and precipitation extremes on global and regional scales. Global changes in temperature extremes include decreases in the number of unusually cold days and nights and increases in the number of unusually warm days and nights.
Other observed changes include lengthening of the growing season, and decreases in the number of frost days. Global temperature extremes have been found to exhibit no significant trend in interlingua variability, but several studies suggest a significant decrease in intra-annual variability. There has been a clear trend to fewer extremely low minimum temperatures in several widely-separated areas in recent decades. Widespread significant changes in extreme high temperature events have not been observed. There is some indication of a decrease in day-to-day temperature variability in recent decades.
In areas where a drought or excessive wetness usually accompanies an El Onion or La Nina, these dry or wet spells have been more intense n recent years. Further, there is some evidence for increasing drought worldwide, however in the U. S. There is no evidence for increasing drought. Len some areas where overall precipitation has increased (e. The mid-high northern latitudes), there is evidence of increases in the heavy and extreme precipitation events. Even in areas such as eastern Asia, it has been found that extreme precipitation events have increased despite total precipitation remaining constant or even decreasing somewhat.
This is related to a decrease in the frequency of precipitation in this region. Many individual studies of various regions show that extra-tropical cyclone activity seems to have generally increased over the last half of the 20th century in the northern hemisphere, but decreased in the southern hemisphere. Furthermore, hurricane activity in the Atlantic has shown an increase in number since 1970 with a peak in 2005. It is not clear whether these trends are multi-decal fluctuations or part of a longer-term trend.
Important are these changes in a longer-term context Pale climatic data are critical for enabling us to extend our knowledge of climatic variability beyond what is measured by modern instruments. Many natural phenomena are climate dependent (such as the growth rate of a tree for example), and as such, provide natural ‘archives’ of climate information. Some useful Paleolithic data can be found in sources as diverse as tree rings, ice cores, corals, lake sediments (including fossil insects and pollen data), splotches (stalactites etc), and ocean sediments.
Some of these, including ice cores and tree rings provide us also with a chronology due to the nature of how they are formed, and so high resolution climate reconstruction is possible in these cases. However, there is not a impressive ‘network’ of Paleolithic data as there is with instrumental coverage, combining different types of Paleolithic records enables us to gain a near-global picture of climate changes in the distant past. For Northern Hemisphere temperature, recent decades appear to be the warmest since at least about 10TH, and the warming since the late 19th century is unprecedented over the last 1000 years.
Older data are insufficient to provide reliable hemispheric temperature estimates. Ice core data suggest that the 20th century has been warm in many parts of the globe, but also that the significance of the warming varies geographically, hen viewed in the context of climate variations of the last millennium. Large and rapid climatic changes affecting the atmospheric and oceanic circulation and temperature, and the hydrological cycle, occurred during the last ice age and during the transition towards the present Holocene period (which began about 10,000 years ago).
Based on the incomplete evidence available, the projected change of 3 to OFF (1. 5 – ICC) over the next century would be unprecedented in comparison with the best available records from the last several thousand years. Sea Level Rising Global mean sea level has been rising at an average rate of 1. Mm/year (plus or minus 0. Mm) over the past 100 years, which is significantly larger than the rate averaged over the last several thousand years. Depending on which greenhouse gas increase scenario is used (high or low) projected sea-level rise is projected to be anywhere from 0. 8 (low greenhouse gas increase) to 0. 59 meters for the highest greenhouse gas increase scenario. However, this increase is due mainly to thermal expansion and contributions from melting alpine glaciers, and does not include any potential contributions from melting ice sheets in Greenland or Antarctica. Larger increases cannot be excluded but our current understanding of ice sheet dynamics renders uncertainties too large to be able to assess the likelihood of large-scale melting of these ice sheets.
Observed changes be explained by natural variability, including changes in solar output Since our entire climate system is fundamentally driven by energy from the sun, it stands to reason that if the sun’s energy output were to change, then so would the climate. Since the advent of space-borne measurements in the late sass, solar output has indeed been shown to vary. With now 28 years of reliable satellite observations there is confirmation of earlier suggestions of an 11 (and 22) year cycle of radiance related to sunspots but no longer term trend in these data.
Based on Paleolithic (proxy) reconstructions of solar radiance there is suggestion of a trend of about +0. 12 W/mm since 1750 which is about half of the estimate given in the last EPIC report in 2001. There is though, a great deal of uncertainty in estimates of solar radiance beyond what can be measured by satellites, and still the contribution of direct solar radiance forcing is small compared to the greenhouse gas component. However, our understanding of the indirect effects of changes in solar output and feedbacks in the climate system is minimal.
There is much need to refine our understanding of key natural forcing mechanisms of the climate, including solar radiance changes, in order to reduce uncertainty in our projections of future and orientation relative to the sun (our orbit) also varies slightly, thereby bringing us closer and further away from the sun in predictable cycles (called Annihilation cycles). Variations in these cycles are believed to be the cause of Earth’s ice-ages (glacial). Particularly important for the development of glacial is the radiation receipt at high northern latitudes.
Diminishing radiation at these latitudes during the summer months would have enabled winter snow and ice cover to persist throughout the year, eventually leading to a permanent snow- or icepack. While Annihilation cycles have tremendous value as a theory to explain ice-ages and long- term changes in the climate, they are unlikely to have very much impact on the decade-century timescale. Over several centuries, it may be possible to observe the effect of these orbital parameters, however for the prediction of climate change in he 21st century, these changes will be far less important than irradiative forcing from greenhouse gases.
Global Warming about the future Due to the enormous complexity of the atmosphere, the most useful tools for gauging future changes are ‘climate models’. These are computer-based mathematical models which simulate, in three dimensions, the climate’s behavior, its components and their interactions. Climate models are constantly improving based on both our understanding and the increase in computer power, though by definition, a computer model is a simplification and simulation of reality, meaning hat it is an approximation of the climate system.
The first step in any modeled projection of climate change is to first simulate the present climate and compare it to observations. If the model is considered to do a good Job at representing modern climate, then certain parameters can be changed, such as the concentration of greenhouse gases, which helps us understand how the climate would change in response. Projections of future climate change therefore depend on how well the computer climate model simulates the climate and on our understanding of how forcing functions will change in the future.
The EPIC Special Report on Emission Scenarios determines the range of future possible greenhouse gas concentrations (and other forcing) based on considerations such as population growth, economic growth, energy efficiency and a host of other factors. This leads a wide range of possible forcing scenarios, and consequently a wide range of possible future climates. According to the range of possible forcing scenarios, and taking into account uncertainty in climate model performance, the EPIC projects a best estimate of global temperature increase of 1. – 4. ICC with a possible range of 1. 1 – 6. C by 2100, depending on which emissions scenario is used. However, this global average will integrate widely varying regional responses, such as the likelihood that land areas will warm much faster than ocean temperatures, particularly those land areas in northern high latitudes (and mostly in the cold season). Additionally, it is very likely that heat waves and other hot extremes will increase.
Precipitation is also expected to increase over the 21st century, particularly at northern mid-high latitudes, though the trends may be more variable in the tropics, with much of the increase coming in ring is expected due to increased evaporation with increased temperatures, resulting in an increased tendency for drought in those regions. Observed Temperature Change: Evidence for warming of the climate system includes observed increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.
The Earth’s average surface temperature, expressed as a linear trend, rose by 0. 74 18 co over the period 1906-2005. The rate of warming over the last half of that period was almost double that for the period as a whole 0. 13 03 co per decade, versus 0. 07 co 02 co per decade). The urban heat island effect is estimated to account for about 0. 002 co of warming per decade since 1900. Temperatures in the lower troposphere have increased between 0. 13 and 0. 22 co (0. 22 and 0. 4 OF) per decade since 1979, according to satellite temperature measurements.
Climate proxies show the temperature to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age. Recent estimates by Anna’s Goddard Institute for Space Studies (GIGS) and the National Climatic Data Center show that 2005 and 2010 tied for the planet’s warmest year since reliable, widespread instrumental measurements became available in the late 19th century, exceeding 1998 by a few hundredths of a degree.
Current estimates by the Climatic Research Unit (CRU) show 2005 as the second warmest year, behind 1998 with 2003 and 2010 tied for third warmest year, however, “the error estimate for individual years is at least ten times larger than the differences between these three years. ” The World Meteorological Organization (WHOM) statement on the status of the global climate in 2010 explains that, “The 2010 nominal value of +0. 53 co ranks Just ahead of those of 2005 (+0. 52 co) and 1998 (+0. 51 co), although the differences between the three years are not statistically significant..
Temperatures in 1998 were unusually warm because the strongest El Onion in the past century occurred during that year. Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 2002 to 009 is consistent with such an episode. Temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0. 25 co per decade against 0. 13 co per decade).
Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation. The Northern Hemisphere warms faster than the Southern Hemisphere because it has more land and because it has extensive areas of seasonal snow and sea-ice cover subject to ice-lobed feedback. Although more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.
The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0. 5 co (0. 9 OF) would still occur. External forcing: Earth) that influence climate. Climate responds to several types of external forcing, such as irradiative forcing due to changes in atmospheric composition (mainly greenhouse gas concentrations), changes in solar luminosity, volcanic eruptions, and variations in Earth’s orbit around the Sun.
Attribution of recent climate change focuses on the first three types of forcing. Orbital cycles vary slowly over tens of thousands of years and at present are in an overall cooling trend which would be expected to lead towards an ice age, but the 20th century instrumental temperature record shows a sudden rise in global temperatures. Particulates and soot Global dimming, a gradual reduction in the amount of global direct radiance at the Earth’s surface, has partially counteracted global warming from 1960 to the present.
The main cause of this dimming is particulates produced by volcanoes and human made pollutants, which exerts a cooling effect by increasing the reflection of incoming sunlight. The effects of the products of fossil fuel combustion-?CO and aerosols-?have largely offset one another in recent decades, so that net warming has been due to the increase in non-CO greenhouse gases such as methane. Irradiative arcing due to particulates is temporally limited due to wet deposition which causes them to have an atmospheric lifetime of one week.
Carbon dioxide has a lifetime of a century or more, and as such, changes in particulate concentrations will only delay climate changes due to carbon dioxide. In addition to their direct effect by scattering and absorbing solar radiation, particulates have indirect effects on the radiation budget. Sulfates act as cloud condensation nuclei and thus lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently Han clouds with fewer and larger droplets, known as the Toomey effect.
This effect also causes droplets to be of more uniform size, which reduces growth of raindrops and makes the cloud more reflective to incoming sunlight, known as the Albrecht effect. Indirect effects are most noticeable in marine stratifies clouds, and have very little irradiative effect on convective clouds. Indirect effects of particulates represent the largest uncertainty in irradiative forcing. [ Soot may cool or warm the surface, depending on whether it is airborne or deposited. Atmospheric soot directly absorb alarm radiation, which heats the atmosphere and cools the surface.
In isolated areas with high soot production, such as rural India, as much as 50% of surface warming due to greenhouse gases may be masked by atmospheric brown clouds. When deposited, especially on glaciers or on ice in arctic regions, the lower surface lobed can also directly heat the surface. The influences of particulates, including black carbon, are most pronounced in the tropics and sub-tropics, particularly in Asia, while the effects of greenhouse gases are dominant in the catastrophic and southern hemisphere. Solar variation Variations in solar output have been the cause of past climate changes.
The effect of changes in solar forcing in recent decades is uncertain, but small, with some studies showing a slight cooling effect, while others studies suggest a slight warming effect. Greenhouse gases and solar forcing affect temperatures in different ways. While both troposphere, an increase in solar activity should warm the stratosphere while an increase in greenhouse gases should cool the stratosphere. Radiation (weather balloon) data show the stratosphere has cooled over the period since observations Egan (1958), though there is greater uncertainty in the early radiations record.
Satellite observations, which have been available since 1979, also show cooling. Related hypothesis, proposed by Henries Sparkman, is that magnetic activity of the sun deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate. Other research has found no relation between warming in recent decades and cosmic rays. The influence of cosmic rays on cloud cover is about a factor of 100 lower than needed to explain the observed changes in loud or to be a significant contributor to present-day climate change.
Studies in 2011 have indicated that solar activity may be slowing, and that the next solar cycle could be delayed. To what extent is not yet clear; Solar Cycle 25 is due to start in 2020, but may be delayed to 2022 or even longer. It is even possible that Sol could be heading towards another Maunder Minimum. While there is not yet a definitive link between solar sunspot activity and global temperatures, the scientists conducting the solar activity study believe that global greenhouse gas emissions would prevent any possible cold snap.