Cloud albedo is a measure of the albedo of a cloud. Higher values indicate that a cloud reflects a larger amount of solar radiation and transmits a smaller amount of radiation. Cloud albedo depends on the total mass of water, the size and shape of the droplets or particles and their distribution in space. Cloud albedo, along with the greenhouse effect of clouds influence the Earth's energy budget. Thick clouds reflect a large amount of incoming solar radiation. Thin clouds tend to transmit most solar radiation. Studies have shown that cloud liquid water path varies with changing cloud droplet size, which may alter the behavior of clouds and their albedo; the variations of the albedo of typical clouds in the atmosphere are dominated by the column amount of liquid water and ice in the cloud. Cloud albedo varies from less than 10% to more than 90% and depends on drop sizes, liquid water or ice content, thickness of the cloud, the sun's zenith angle; the smaller the drops and the greater the liquid water content, the greater the cloud albedo, if all other factors are the same.
Addition of cloud nuclei by pollution can lead to an increase in solar radiation reflected by clouds. Increasing aerosol concentration and aerosol density increases cloud droplet concentration, decreases cloud droplet size, increases cloud albedo. In macrophysically identical clouds, a cloud with few larger drops will have a lower albedo than a cloud with more smaller drops; the cloud albedo increases with the total water content or depth of the cloud and with the solar zenith angle. The variation of albedo with zenith angle is most rapid when the sun is near the horizon, least when the sun is overhead. Absorption of solar radiation by plane-parallel clouds decreases with increasing zenith angle because radiation, reflected to space at the higher zenith angles penetrates less into the cloud and is therefore less to be absorbed
Radiative forcing or climate forcing is the difference between insolation absorbed by the Earth and energy radiated back to space. The influences that cause changes to the Earth’s climate system altering Earth’s radiative equilibrium, forcing temperatures to rise or fall, are called climate forcings. Positive radiative forcing means Earth receives more incoming energy from sunlight than it radiates to space; this net gain of energy will cause warming. Conversely, negative radiative forcing means that Earth loses more energy to space than it receives from the sun, which produces cooling. Radiative forcing is quantified at the tropopause or at the top of the atmosphere in units of watts per square meter of the Earth's surface. Positive forcing warms the system. Causes of radiative forcing include changes in insolation and the concentrations of radiatively active gases known as greenhouse gases, aerosols. All of the energy that affects Earth's climate is received as radiant energy from the Sun; the planet and its atmosphere absorb and reflect some of the energy, while long-wave energy is radiated back into space.
The balance between absorbed and radiated energy determines the average global temperature. Because the atmosphere absorbs some of the re-radiated long-wave energy, the planet is warmer than it would be in the absence of the atmosphere: see greenhouse effect; the radiation balance is altered by such factors as the intensity of solar energy, reflectivity of clouds or gases, absorption by various greenhouse gases or surfaces and heat emission by various materials. Any such alteration is a radiative forcing, changes the balance; this happens continuously as sunlight hits the surface and aerosols form, the concentrations of atmospheric gases vary and seasons alter the groundcover. The Intergovernmental Panel on Climate Change AR4 report defines radiative forcings as: "Radiative forcing is a measure of the influence a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism.
In this report radiative forcing values are for changes relative to preindustrial conditions defined at 1750 and are expressed in Watts per square meter." In simple terms, radiative forcing is "...the rate of energy change per unit area of the globe as measured at the top of the atmosphere." In the context of climate change, the term "forcing" is restricted to changes in the radiation balance of the surface-troposphere system imposed by external factors, with no changes in stratospheric dynamics, no surface and tropospheric feedbacks in operation, no dynamically induced changes in the amount and distribution of atmospheric water. Radiative forcing can be used to estimate a subsequent change in steady-state surface temperature arising from that forcing via the equation: Δ T s = λ Δ F where λ is denoted the climate sensitivity parameter with units K/, ΔF is the radiative forcing in W/m2. A typical value of λ, 0.8 K/, gives an increase in global temperature of about 1.6 K above the 1750 reference temperature due to the increase in CO2 over that time, predicts a further warming of 1.4 K above present temperatures if the CO2 mixing ratio in the atmosphere were to become double its pre-industrial value.
Radiative forcing can be estimated in different ways for different components. For solar irradiance, the radiative forcing is the change in the average amount of solar energy absorbed per square meter of the Earth's area. Since the Earth's cross-sectional area exposed to the Sun is equal to 1/4 of the surface area of the Earth, the solar input per unit area is one quarter the change in solar intensity; this must be multiplied by the fraction of incident sunlight, absorbed, F=, where R is the reflectivity, of the Earth. The albedo is 0.3, so F is equal to 0.7. Thus, the solar forcing is the change in the solar intensity divided by 4 and multiplied by 0.7. A change in albedo will produce a solar forcing equal to the change in albedo divided by 4 multiplied by the solar constant. For a greenhouse gas, such as carbon dioxide, radiative transfer codes that examine each spectral line for atmospheric conditions can be used to calculate the change ΔF as a function of changing concentration; these calculations might be simplified into an algebraic formulation, specific to that gas.
For instance, a proposed simplified first-order approximation expression for carbon dioxide would be: Δ F = 5.35 × ln C C 0 W m − 2 where C is the CO2 concentration in parts per million by volume and C0 is the reference concentration. There is the claim of a relationship between carbon dioxide and radiative forcing is logarithmic, at concentrations up to around eight times the current value, thus increased concentrations have a progressively smaller warming effect; some claim th
East Coast of the United States
The East Coast of the United States known as the Eastern Seaboard, the Atlantic Coast, the Atlantic Seaboard, is the coastline along which the Eastern United States meets the North Atlantic Ocean. The coastal states that have shoreline on the Atlantic Ocean are, from north to south, New Hampshire, Rhode Island, New York, New Jersey, Maryland, North Carolina, South Carolina and Florida; the place name "East Coast" derives from the idea that the contiguous 48 states are defined by two major coastlines, one at the western edge and one on the eastern edge. Other terms for referring to this area include the "Eastern Seaboard", "Atlantic Coast", "Atlantic Seaboard"; the fourteen states that have a shoreline on the Atlantic Ocean are, from north to south, the U. S. states of Maine, New Hampshire, Rhode Island, New York, New Jersey, Maryland, North Carolina, South Carolina and Florida. In addition and the District of Columbia border tidal arms of the Atlantic; the states of Alabama, Mississippi and Texas, as well as the territories of Puerto Rico, the US Virgin Islands, Navassa Island have Atlantic coastline, but are not included in the definition.
Although Vermont and West Virginia have no Atlantic coastline, they are sometimes grouped with the Eastern Seaboard states because of their locations in New England and the Old South, their history as part of the land base of the original Thirteen Colonies. The original thirteen colonies of Great Britain in North America all lay along the East Coast. Two additional U. S. states on the East Coast were not among the original thirteen colonies: Florida. The Middle Colonies had been owned by the Dutch as New Netherland, until they were captured by the English in the mid-to-late 17th century. There are three basic climate regions on the East Coast according to the Köppen climate classification from north to south based on the monthly mean temperature of the coldest month: The region from northern Maine south to northern Rhode Island and Connecticut has a continental climate, with warm summers, cold and snowy winters; the area from southern Rhode Island and New York City south to central Florida has a temperate climate, with long, hot summers and cold winters with occasional snow in the northern portions, milder winters in the southern portions.
Around south-central Florida southward has a tropical climate, frost free and is warm to hot all year. Average monthly precipitation ranges from a slight late fall maximum from Massachusetts northward, to a slight summer maximum in the Mid-Atlantic states from southern Connecticut south to Virginia, to a more pronounced summer maximum from Cape Hatteras, North Carolina, southward along the Southeastern United States coast to Savannah, Georgia; the Florida peninsula has a sharp wet-summer/dry-winter pattern, with 60 to 70 percent of precipitation falling between June and October in an average year, a dry, sunny late fall and early spring. Although landfalls are rare, the Eastern seaboard is susceptible to hurricanes in the Atlantic hurricane season running from June 1 to November 30, although hurricanes can occur before or after these dates. Hurricanes Hazel, Bob, Irene and most Florence are some of the more significant storms to have affected the region; the East Coast is a passive margin coast.
It has been shaped by the Pleistocene glaciation in the far northern areas from New York City northward, with offshore islands such as Nantucket, Block Island, Fishers Island, the nearly peninsular Long Island and New York City's Staten Island the result of terminal moraines, with Massachusetts' unique peninsula of Cape Cod showing the additional action of outwash plains, besides terminal moraines. The coastal plain broadens southwards, separated from the Piedmont region by the Atlantic Seaboard fall line of the East Coast rivers marking the head of navigation and prominent sites of cities; the coastal areas from Long Island south to Florida are made up of barrier islands that front the coastal areas, with the long stretches of sandy beaches. Many of the larger capes along the lower East Coast are in fact barrier islands, like the Outer Banks of North Carolina and Cape Canaveral, Florida; the Florida Keys provide the only coral reefs on the US mainland. In 2010, the population of the states which have shoreline on the East Coast was estimated at 112,642,503.
The East Coast is the most populated coastal area in the United States. The primary Interstate Highway along the East Coast is Interstate 95, completed in 2018, which replaced the historic U. S. Route 1, the original federal highway that traversed all East Coast states, except Delaware. By water, the East Coast is connected from Boston, Massachusetts to Miami, Florida, by the Intracoastal Waterway known as the East Coast Canal, completed in 1912. Amtrak's Downeaster and Northeast Regional offer the main passe
Cloud condensation nuclei
Cloud condensation nuclei or CCNs are small particles 0.2 µm, or 1/100th the size of a cloud droplet on which water vapor condenses. Water requires a non-gaseous surface to make the transition from a vapour to a liquid. In the atmosphere, this surface presents itself as tiny liquid particles called CCNs; when no CCNs are present, water vapour can be supercooled at about −13°C for 5–6 hours before droplets spontaneously form. In above freezing temperatures the air would have to be supersaturated to around 400% before the droplets could form; the concept of cloud condensation nuclei is used in cloud seeding, that tries to encourage rainfall by seeding the air with condensation nuclei. It has further been suggested that creating such nuclei could be used for marine cloud brightening, a climate engineering technique. A typical raindrop is about 2 mm in diameter, a typical cloud droplet is on the order of 0.02 mm, a typical cloud condensation nucleus is on the order of 0.0001 mm or 0.1 µm or greater in diameter.
The number of cloud condensation nuclei in the air can be measured and ranges between around 100 to 1000 per cubic centimetre. The total mass of CCNs injected into the atmosphere has been estimated at 2x1012 kg over a year's time. There are many different types of atmospheric particulates that can act as CCN; the particles may be composed of dust or clay, soot or black carbon from grassland or forest fires, sea salt from ocean wave spray, soot from factory smokestacks or internal combustion engines, sulfate from volcanic activity, phytoplankton or the oxidation of sulfur dioxide and secondary organic matter formed by the oxidation of volatile organic compounds. The ability of these different types of particles to form cloud droplets varies according to their size and their exact composition, as the hygroscopic properties of these different constituents are different. Sulfate and sea salt, for instance absorb water whereas soot, organic carbon and mineral particles do not; this is made more complicated by the fact that many of the chemical species may be mixed within the particles.
Additionally, while some particles do not make good CCN, they do act as ice nuclei in colder parts of the atmosphere. The number and type of CCNs can affect the precipitation amount and radiative properties of clouds as well as the amount and hence have an influence on climate change. There is speculation that solar variation may affect cloud properties via CCNs, hence affect climate. Sulfate aerosol act as CCNs; these sulfate aerosols form from the dimethyl sulfide produced by phytoplankton in the open ocean. Large algal blooms in ocean surface waters occur in a wide range of latitudes and contribute considerable DMS into the atmosphere to act as nuclei; the idea that an increase in global temperature would increase phytoplankton activity and therefore CCN numbers was seen as a possible natural phenomenon that would counteract climate change. An increase of phytoplankton has been observed by scientists in certain areas but the causes are unclear. A counter-hypothesis is advanced in The Revenge of the book by James Lovelock.
Warming oceans are to become stratified, with most ocean nutrients trapped in the cold bottom layers while most of the light needed for photosynthesis in the warm top layer. Under this scenario, deprived of nutrients, marine phytoplankton would decline, as would sulfate cloud condensation nuclei, the high albedo associated with low clouds; this is known as the CLAW hypothesis but no conclusive evidence to support this has yet been reported. Bergeron process Evapotranspiration Global dimming Seed crystal Water cycle www.grida.no
Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming. Though earlier geological periods experienced episodes of warming, the term refers to the observed and continuing increase in average air and ocean temperatures since 1900 caused by emissions of greenhouse gasses in the modern industrial economy. In the modern context the terms global warming and climate change are used interchangeably, but climate change includes both global warming and its effects, such as changes to precipitation and impacts that differ by region. Many of the observed warming changes since the 1950s are unprecedented in the instrumental temperature record, in historical and paleoclimate proxy records of climate change over thousands to millions of years. In 2013, the Intergovernmental Panel on Climate Change Fifth Assessment Report concluded, "It is likely that human influence has been the dominant cause of the observed warming since the mid-20th century."
The largest human influence has been the emission of greenhouse gases such as carbon dioxide and nitrous oxide. Climate model projections summarized in the report indicated that during the 21st century, the global surface temperature is to rise a further 0.3 to 1.7 °C to 2.6 to 4.8 °C depending on the rate of greenhouse gas emissions and on climate feedback effects. These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing. Future climate change effects are expected to include rising sea levels, ocean acidification, regional changes in precipitation, expansion of deserts in the subtropics. Surface temperature increases are greatest in the Arctic, with the continuing retreat of glaciers and sea ice. Predicted regional precipitation effects include more frequent extreme weather events such as heat waves, wildfires, heavy rainfall with floods, heavy snowfall. Effects directly significant to humans are predicted to include the threat to food security from decreasing crop yields, the abandonment of populated areas due to rising sea levels.
Environmental impacts appear to include the extinction or relocation of ecosystems as they adapt to climate change, with coral reefs, mountain ecosystems, Arctic ecosystems most threatened. Because the climate system has a large "inertia" and greenhouse gases will remain in the atmosphere for a long time, climatic changes and their effects will continue to become more pronounced for many centuries if further increases to greenhouse gases stop. Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, possible future climate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change, whose ultimate objective is to prevent dangerous anthropogenic climate change. Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 °C compared to pre-industrial levels, with efforts made to limit warming to 1.5 °C. Some scientists call into question climate adaptation feasibility, with higher emissions scenarios, or the two degree temperature target.
Public reactions to global warming and concern about its effects are increasing. A 2015 global survey showed that a median of 54% of respondents consider it "a serious problem", with significant regional differences: Americans and Chinese are among the least concerned. Multiple independently produced datasets confirm that between 1880 and 2012, the global average surface temperature increased by 0.85 °C. Since 1979 the rate of warming has doubled. Climate proxies show the temperature to have been 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. Although the increase of the average near-surface atmospheric temperature is used to track global warming, over 90% of the additional energy stored in the climate system over the last 50 years has accumulated in the oceans; the rest warmed the continents and the atmosphere. The warming evident in the instrumental temperature record is consistent with a wide range of observations, as documented by many independent scientific groups.
Examples include sea level rise, widespread melting of snow and land ice, increased heat content of the oceans, increased humidity, the earlier timing of spring events, e.g. the flowering of plants. Global warming refers with the amount of warming varying by region. Since 1979, global average land temperatures have increased about twice as fast as global average ocean temperatures; this is due to the larger heat capacity of the oceans and because oceans lose more heat by evaporation. Where greenhouse gas emissions occur does not impact the location of warming because the major greenhouse gases persist long enough to diffuse across the planet, although localized black carbon deposits on snow and ice do contribute to Arctic warming; the Northern Hemisphere and North Pole have heated much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, its arrangement around the Arctic Ocean has resulted in the maximum surface area flipping from reflective snow and ice cover to ocean and land surfaces that absorb more sunlight.
Contrails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure at aircraft cruise altitudes several miles above the Earth's surface. Contrails are composed of water, in the form of ice crystals; the combination of water vapor in aircraft engine exhaust and the low ambient temperatures that exist at high altitudes allows the formation of the trails. Impurities in the engine exhaust from the fuel, including sulfur compounds provide some of the particles that can serve as sites for water droplet growth in the exhaust and, if water droplets form, they might freeze to form ice particles that compose a contrail, their formation can be triggered by changes in air pressure in wingtip vortices or in the air over the entire wing surface. Contrails, other clouds directly resulting from human activity, are collectively named homogenitus. Depending on the temperature and humidity at the altitude the contrails form, they may be visible for only a few seconds or minutes, or may persist for hours and spread to be several miles wide resembling natural cirrus or altocumulus clouds.
Persistent contrails are of particular interest to scientists because they increase the cloudiness of the atmosphere. The resulting cloud forms are formally described as homomutatus, may resemble cirrus, cirrocumulus, or cirrostratus, are sometimes called cirrus aviaticus. Persistent spreading contrails are suspected to have an effect on global climate; the main products of hydrocarbon fuel combustion are water vapor. At high altitudes this water vapor emerges into a cold environment, the local increase in water vapor can raise the relative humidity of the air past saturation point; the vapor condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails; the time taken for the vapor to cool enough to condense accounts for the contrail forming some distance behind the aircraft. At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation; the exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to condense rapidly.
Exhaust contrails form at high altitudes. They can form closer to the ground when the air is cold and moist. A 2013–2014 study jointly supported by NASA, the German aerospace center DLR, Canada's National Research Council NRC, determined that biofuels could reduce contrail generation; this reduction was explained by demonstrating that biofuels produce fewer soot particles, which are the nuclei around which the ice crystals form. The tests were performed by flying a DC-8 at cruising altitude with a sample-gathering aircraft flying in trail. In these samples, the contrail-producing soot particle count was reduced by 50 to 70 percent, using a 50% blend of conventional Jet A1 fuel and HEFA biofuel produced from camelina; as a wing generates lift, it causes a vortex to form at the wingtip, at the tip of the flap when deployed These wingtip vortices persist in the atmosphere long after the aircraft has passed. The reduction in pressure and temperature across each vortex can cause water to condense and make the cores of the wingtip vortices visible.
This effect is more common on humid days. Wingtip vortices can sometimes be seen behind the wing flaps of airliners during takeoff and landing, during landing of the Space Shuttle; the visible cores of wingtip vortices contrast with the other major type of contrails which are caused by the combustion of fuel. Contrails produced from jet engine exhaust are seen at high altitude, directly behind each engine. By contrast, the visible cores of wingtip vortices are seen only at low altitude where the aircraft is travelling after takeoff or before landing, where the ambient humidity is higher, they trail behind the wingtips and wing flaps rather than behind the engines. At high-thrust settings the fan blades at the intake of a turbofan engine reach transonic speeds, causing a sudden drop in air pressure; this creates the condensation fog, observed by air travelers during takeoff. The tips of rotating surfaces sometimes produce visible contrails. Contrails, by affecting the Earth's radiation balance, act as a radiative forcing.
Studies have found that contrails trap outgoing longwave radiation emitted by the Earth and atmosphere at a greater rate than they reflect incoming solar radiation. NASA conducted a great deal of detailed research on atmospheric and climatological effects of contrails, including effects on ozone, ice crystal formation, particle composition, during the Atmospheric Effects of Aviation Project. Global radiative forcing has been calculated from the reanalysis data, climatological models and radiative transfer codes, it is estimated to amount to 0.012 W/m² for 2005, with an uncertainty range of 0.005 to 0.026 W/m², with a low level of scientific understanding. Therefore, the overall net effect of contrails is positive, i.e. a warming effect. However, the effect varies daily and annually, overall the magnitude of the forcing is not well known: Globally, values range from 3.5 mW/m² to 17 mW/m². Other studies have determined that night flights are responsible for the warming effect: while accounting for only 25% of daily air traffic, they contribute 60 to 80% of contrail radiative forcing