1.How is Earth’s Climate Defined?
Climate, on the other hand, can be related to the statistical probability that any day during the year will be similar to the same day in previous or following years. Climate change is both natural and normal, and it is driven by many different factors acting over different timescales
• Temperatures, highs, lows, gradients (vertical and horizontal)
Over the past 100 years, global temperature has been risingat a rate that is slow in terms of a human lifespan but rapidenough to worry climate scientists. ( I emailed TA for this question and I will update my notes after she gave my answer)
• Precipitation amount and temporal patterns
The amount of water vapor that air can hold increases rapidly with temperature, at a rate of about 7% per 1°C, and as part of a natural water cycle, this will inevitably lead to an increase in rainfall.
Changing patterns of Climate:
Global pattern emerging: 1. Single event could be due to natural causes 2. New trend: fewer cold days, more warm nights, fewer frost days, more heat waves, more wildfires, longer growing season
changes in precipitation, water vapor in air increases ~7% per1centigrade, more intense rainfall, increased flooding.
Some areas will see increased drought: Africa (the Sahel), Amazon Basin, South Africa, Southern Europe
• Storm types
Hurricane: increase in intensity likely, increase in frequency less certain, formation depends on many factor: Atlantic multidecadal oscillation which can increase regional storm frequency. El Nino, which decreases storm frequency
2. Evidence of climatic changes
Subsequent observations, compiled from ground stations, weather balloons, and weather satellites, confirm that Earth is warming over most of its surface, but warming is uneven.
• How fast
Compared to the average temperature from 1901–2000, surface temperature over the land is increasing much faster than over the oceans (0.85°C vs. 0.37°C) and while much of the Northern Hemisphere at high latitudes is getting warmer (the Arctic is warming at twice the global average rate), parts of Antarctica may be getting colder. We also discuss several other topics like How many heterozygotes are expected to be in the new population in the next generation?
• For how long
The Hadley Centre Coupled Model, version 3 (HadCM3) climate model shows that the Northern Hemisphere experienced the greatest amount of warming between 1995–2004 and projects a further rise in temperature in excess of 5°C–6°C (9.0°–10.8°F) over high northern latitudes between 2070–2100 if heat trapping greenhouse gas emissions are not
3. What Control’s Earth Climate System Behavior
• Radiation In vs Radiation Out
Greenhouse Gas Forcing:
Carbon Dioxide: is responsible for 56% of greenhouse gas forcing and contributes around 1.82 Wm–2 toward an estimated total of 2.83 Wm–2 from the WMGHGs. We also discuss several other topics like What is Eye tracking?
Methane; It is estimated that methane gas is responsible for 16% of greenhouse gas forcing and that it con tributes around 0.48 Wm–2 toward the total greenhouse gas forcing of 2.83 Wm–2 from the longlived green house gases (excluding water vapor). We also discuss several other topics like What are Consumer magazines?
Nitrous Oxide: at over 319 ppb, is considered to be responsible for around 5% of greenhouse gas forcing and contributes around 0.17 Wm–2 toward the total greenhouse gas forcing of 2.83 Wm–2
Ozone: contributes 0.40 Wm–2 toward green house gas forcing in the troposphere, and ozone loss due to CFCs contributes −.10 Wm–2 towards cooling of the stratosphere.
Aerosols：produced by industrial and volcanic processes are tiny particles of solid and liquid that become suspended in the atmosphere and act to partially block the passage of sunlight.) Albedo (Albedo is a measure of how strongly sunlight is reflected by Earth’s
surface and atmosphere. In general, clouds, snow, ice, and deserts have higher albedo than forests, lakes, oceans, tundra, and agricultural land.
• Net Imbalance today (~1.65W/m2)
Net radiation = incoming radiation – outgoing radiation
• Where the E. fluxes in and fluxes out are greatest We also discuss several other topics like what are the The Scientific Methods?
We also discuss several other topics like what is Electromagnetic Radiation?
• Factors that influence the flux of energy in and out
Many different factors affect the balance at the top of the atmosphere. Some, such as the amount of energy from the sun, anthropogenic greenhouse gases, black carbon, and aerosols, act to force climate change away from a state of quasi equilibrium. Others, such as clouds, albedo, sea ice, and the natural release of natural greenhouse gases, are a response to climate forcing and can act to reinforce climate change (positive feedback) or ameliorate the impact of climate change (negative feedback). If you want to learn more check out What is cellular differentiation?
Positive feedback from water vapor, natural green house gases, changes in albedo, and some kinds of cloud cover enhance the effect. The negative forcing from aerosols, natural aerosols, black carbon, and other kinds of cloud cover ameliorate the impact, but there is still a net imbalance of radiation at the top of the atmosphere that is growing and is enough to increase the risks associated with climate change over the following century
• Work that is done (Law of Thermodynamics)
Energy is conserved between a system and its surroundings when work is done.
• Changes in Earth’s Orbit (on longer time scales)
On a timescale of tens of thousands to hundreds of thousands of years, Earth’s orbit follows welldefined cycles that determine how the amount of solar radiation reaching the top of the atmosphere changes with the seasons. The amount and global distribution of
this energy waxes and wanes with small changes in the tilt of Earth’s axis of rotation (obliquity), the direction of that tilt (precession), and shape of the orbit (eccentricity).
atmosphere pressure: Force per unit area exerted by gases
average sea level pressure – 1013.25mb
Dalton’s Law sum of partial pressures
The “weight” of overlying air
A function of density and temperature
• Atmospheric Circulation (How, where, when)
On a smooth nonrotating planet, the pattern of atmospheric circulation would be simple. Air heated at the equator would rise toward the top of the troposphere, move toward the
poles, cool, descend, and flow back along the surface toward the equator. However, this is not what we observe with our planet. Atmospheric circulation is made complex by the effect of Earth spinning on its axis, at over 1,600 km hr–1 (994 mph) near the equator, and the presence of oceans, plateaus, and mountains that interrupt the flow of air.
Despite this complexity, years of data give us an accurate picture of the pattern of atmospheric circulates over time. These data reveal complex patterns of vertical convection and lateral advection in the tropo sphere that are effective at transferring energy from lower to higher latitudes and maintain an overall balance in global temperature
• Ocean Circulation (How, where, when)
Global circulation begins where cold, dense, relatively lowsalinity Arctic seawater sinks from the surface and flows southward along the ocean floor at depth. It crosses the equator (in contrast to circulation in the atmosphere) and flows toward the South Pole, where is joined by a flow of even colder, dense water from the Antarctic. This process is known as thermohaline circulation because it is driven by changes in both water temperature (thermo) and salinity. This flow of deep cold water continues until it slowly rises toward the surface and warms in both the Pacific and Indian Oceans. Surface currents then complete the global circulation by transferring this warm water back toward the poles. In this way, the tropics are cooled and the poles are warmed, and the energy balance of the climate system is maintained.
• Relative amounts of energy carried by Ocean vs Atmosphere
Energy is transported through Earth’s climate system in different forms. In the atmosphere water vapor plays a critical role because of the vast amounts of heat required to turn liquid water into water vapor. The energy released into the atmo sphere by the condensation of water vapor is the fuel that drives the global climate engine. The heat capacity of water is a critical factor in the oceans, as water is able to absorb and retain a large amount of energy with only a small rise in
temperature. Ocean currents then transport this water to higher latitudes, where this energy is transferred to warm the atmosphere.
• Time scales of energy transfer by the Atmosphere vs the Ocean
The physical interaction between the atmosphere and oceans is complex, producing long term oscillations in the rate of exchange of energy. These major oceanatmosphere oscillations such as El Niño and the Pacific Decadal Oscillation take years to complete and are so large that they can mask any underlying trend of global climate change for more than a decade.
• Future Projections (IPCC)
The influential United Nations Intergovernmental Panel on Climate Change (IPCC) projects how greenhouse gas emissions may change in the future. The IPCC makes these projections by using economic models to illustrate a number of contrasting “storylines” that it outlines in its Special Report: Emissions Scenarios
• Emission Scenarios AR4 (storyline A1, A2, B1, B2)
A1: The A1 storyline and scenario family is based on a future world of very rapid economic growth and a global population that peaks in midcentury but declines thereafter, and foresees the rapid introduction of new and more efficient technologies.
A2: The A2 storyline and scenario family is based on a very heterogeneous world where global population continues to increase, and economic growth is more regionally oriented, more fragmented, and slower to develop than in other storylines.
B1: The B1 storyline and scenario family is based on a more convergent world where global population grows as rapidly as in the A1 storyline, but where rapid changes in economic structure focus on the development of a service and informationbased
economy that uses less raw materials and encourages the introduction of clean and resourceefficient technologies.
B2: The B2 storyline and scenario family is based on a less likely world where there is an intermediate level of economic development, global population grows more slowly, and there is an emphasis on local solutions to economic, social, and environ mental problems.
• Represenative Concentration Pathways by the year 2300 (RCP4.5, RCP6,
Four new Representative Concentration Pathways (RCPs) are proposed:
The RCP3_PD model assumes that radiative forcing peaks by 2050 at ca. 3 Wm2 and decreases to 2.6 Wm2 by 2100.
The RCP4.5 model assumes we are close to stabilizing radiative forcing at 4.5 Wm2 in 2100 and that carbon dioxide concentrations, and radiative forcing are held constant after 2100.
The RCP6 model assumes that radiative forcing reaches 6 Wm2 by 2100 before declining to stabilize at 4.5 Wm2 .
The RCP8.5 model assumes that radiative forcing is still increasing and that emissions are still high. This results in very high radiative forcing of 16 Wm2 and a concentration of carbon dioxide in the atmosphere as high as 3,000 parts per million.
• Projected Warming
Climate models and geological evidence suggest that doubling the level of carbon dioxide in the atmosphere will result in a global rise in temperature of at least 3 C. This is
close to the level where some models suggest that inherent, chaotic instability in the climate system (tipping points) could lead to very rapid, damaging, and permanent climate change.