climate change
Which season(s) a greenhouse warming should have the greatest relative effects of surface temperatures?
winter
greenhouse effect
"Reduced Cooling"; increased absorption of outgoing longwave radiation reduces the amount of radiation lost in the air
Method for determining past atmospheric concentrations of CO2.
Analysis of air trapped in Antarctic ice sheets through ice from different periods rings of deposition in ice go back and gives records deeper and deeper within the core bring into the lab in freezing conditions and take slices and date them there are air bubbles that are trapped melt the ice, trap the air bubbles and analyze the air
Global warming and changes in ocean circulation
As ice melts in regions such as Greenland, there is a larger input of fresh water into oceans such as North Atlantic; the water flowing south decreases salinity (i.e. lower density), so waters cannot sink; thus, this slows down transport and thermohaline circulation of water
trends in global average precipitation over the past century
As sea surface temperatures have been increasing (more thermal energy), there has been an increase in humidity (more water is being evaporated); thus, there has also been an increase in mean global precipitation increase mean annual temp, there is increase thermal energy for evaporation, so overall, there has been an increase in global precipitation temperature and precipitation have both increased amount of water that can be held in a piece of air is a function of temperature saturation vapor pressure, increasing temperature, more moisture as humidity increases, more precipitation in general, overall decrease in snow accumulation if you keep temps below freezing, but closer to 0, increase saturation vapor pressure, which means more precipitation
During which period(s) of the day should a greenhouse warming have the greatest relative effects of surface temperatures? Diurnal patterns of surface energy balance
At night, temperatures are declining as a result of decreased outgoing longwave radiation; greenhouse gases will make night time temperatures warmer by absorbing the outgoing longwave radiation (keeping heat in)
Major causes for the rise in atmospheric CO2 over the past 150 years
Burning of Fossil fuels Forest clearing/burning
Historical trends in atmospheric CO2 since the Industrial Revolution (past 150-300 years).
CO2 concentrations have increased by over 45% since pre-industrial times due to increased coal burning and use of fossil fuels consistent upward trend, higher in the past 150 years
Role of thermocline in limiting the uptake of CO2 by oceans.
CO2 diffuses slowly in water; since vertical mixing doesn't occur on deeper ocean levels, the amount of CO2 uptake is limited because C02 is only on the ocean surface, you have to mix it up and get it deeper down major constraint on getting C02 from air to ocean restricts it for 300- 400 meters down
trends in extreme temperatures over the past 50 years
Cold nights and cold days have been getting warmer, and warm nights and warm days have also been getting warmer shows deviations from the overall trend cold nights/ days have been declining warm nights/ days on the rise changes in minimum and maximum temps
Influence of increasing ocean acidity on marine organisms.
Declining pH levels have caused a decrease in mineral forms of calcium carbonate, which are necessary for formation of shells in marine invertebrates C02 reacts with water, forms carbonates and bicarbonates and releases hydrogen ions C02 goes up and PH goes down the water becomes more acidic kills the animals
Global warming and feedbacks on surface albedo (reduction in snow/ice cover)
Decrease in ice cover decreases the reflectivity (albedo), so more incoming radiation is being absorbed by the surface; sets up a positive feedback Reducing snow cover on land also decreases albedo, resulting in higher surface temperatures
Role of ocean thermohaline circulation on the uptake of CO2 by oceans.
Diffusion controls the uptake of CO2 by oceans Increased CO2 results in increased rate of diffusion into surface ocean waters Does not affect ocean NPP The transfer of carbon from surface waters to deep waters of ocean depends on global patterns of ocean circulation (occurs over 100s of years)
During which season(s) should a greenhouse warming have the greatest relative effects of surface temperatures? Seasonal patterns of surface energy balance
During the winter, there is more outgoing longwave radiation being released into atmosphere than shortwave coming in Increasing greenhouse gases, which absorb outgoing longwave radiation, will have a greater effect on temperatures by keeping heat in the air
FACE experiments
Free Air Enrichment Experiences control the free air and the C02 content huge towers that emit carbon when the carbon levels are too low to promote growth study the difference in NPP Experiments testing levels of CO2 in atmosphere on plant growth in natural environments
greenhouse gases
Gases such as water vapor and CO2 do not absorb incoming solar radiation, but are effective at absorbing outgoing longwave radiation.
primary causes of past and recent sea-level rise
Glacial ice melting and thermal expansion (Oceans are getting warmer sea level was 100 meters lower than today because ice has melted. it's been rising 2 millimeters per year on average (bc of rising temp) if you heat something up, it expands, so sea level rises 1.3 millimeters because of melting glaciers
Changes in global average land - ocean surface temperature over the past century (since 1880)
Global annual temperature has increased at an average rate of 0.07 degrees C per decade since 1880 and at an average rate of 0.17 deg C since 1970 Over the past 30 years, Earth has warmed by about 0.6C or 1.08F Definite geographic variation Each of the last three decades has been successively warmer- 2015 warmest year on record
GCM: General Circulation Models / Global Circulation Models
Global, grid-based models that are divided into pixels based on latitude and longitude (horizontal) as well as height and pressure (vertical) Look at all aspects of Earth's system (atmosphere, land-surface processes, ocean processes, radiation, etc) to evaluate changes in Earth's climate and predict future patterns Study the effects of natural forces and anthropogenic (human) forces on climate change
IPCC Report - Cause of "recent" warming
Human influence (due to rising concentrations of greenhouse gases)
In which region(s) should a greenhouse warming have the greatest relative effects of surface temperatures? Geographic pattern of surplus/deficit in annual average net radiation balance Geographic patterns of atmospheric water vapor
In high latitudes where there is a deficit in net radiation, there will be greater effects on surface temperatures, as greenhouse gases absorb outgoing radiation Water vapor is also low in polar regions, which increases relative contribution of carbon dioxide on the overall greenhouse effect
Global warming and feedbacks to global carbon cycle NPP Decomposition
Increased surface temperatures result in further melting of permafrost, warming up the soil and increasing decomposition rates (NPP), thus increasing CO2 emissions
Influence of rising atmospheric CO2 on NPP in terrestrial ecosystems.
Increasing levels of atmospheric CO2 cause an increase in terrestrial NPP (rates of photosynthesis increase as flow rate of CO2 into leaves increases) trapping the outgoing radiation
Global carbon cycle - main reservoirs and fluxes (atmosphere, oceans, land, etc.)
Most of carbon is reserved in geosphere (earth's crust, rocks/minerals); oceans hold mostly inorganic dissolved carbon at great depths; carbon in terrestrial ecosystems and small amount is in atmosphere Fluxes occur due to processes of photosynthesis, respiration, decomposition and human activity releases: emission from fossil fuels is the greatest land: use change very little but upward trend accumulation: very little from terrestrial ecosystems ocean uptakes second most carbon atmospheric accumulates the most carbon
climate change and the decline of sea ice and glaciers
Over the last 20 years, Greenland and Antarctic ice sheets have been shrinking along with glaciers and Arctic sea ice due to more of it melting during the summer as temperatures have increased relatively well behaved- wide variety of shifts in C02 levels past 150 years - getting warmer than it has been • In general, there has been a decrease in snow accumulation. • However in some areas, we have had an increase in amount of snow even though temperatures are a little warmer (however they are still below freezing so rain can fall as snow). This creates more water able to be in the air because the temperature is a little warmer (even though below freezing) but the saturation vapor pressure (I think) in the air is higher and can hold more water.
Processes controlling the exchange of CO2 between terrestrial ecosystems and the atmosphere.
Photosynthesis-- moves CO2 from the atmosphere into the biosphere Respiration--brings CO2 from biosphere to the atmosphere
How does increasing greenhouse gases influence surface temperatures? Reduction of outgoing longwave radiation
Reduction of outgoing longwave radiation (greenhouse gases absorb outgoing longwave radiation) traps heat in atmosphere, causing an increase in surface temperatures
Climate change and sea-level rise Past 150 years
Sea levels have been rising and the rate at which they have been increasing has accelerated • Past 150 years: Continued increase in sea-level and the rate of sea-level rise has been on the increase. Put into context: Earth's climate has changed dramatically over its history. • The rise in global surface temperature appears related to rising atmospheric concentrations of greenhouse gases (CO2)
climate change and extreme weather events- hurricanes
The increase in mean annual tropical sea surface temperature has corresponded to a 60% increase in a tropical cyclone (hurricane)'s potential destructiveness (warmer surface waters resulted in stronger low pressure systems, leading to higher wind speeds) topical cyclones, form off the West Coast of Africa travel in clockwise fashion to Golf of Mexico low pressure system, draw in the wind in Northern Hemisphere: travel counter clockwise greater pressure, stronger the winds flow into it destructive power has increased 70 percent intensity of hurricane driven by surface temperature of the ocean greater precipitation/ evaporation/ winds not an increase in hurricanes, increase in temperature, destructiveness destructive power has increased around 70 percent; the percentage of hurricanes classified as Category 4 or 5 has increased over the same period
CO2 fertilization effect (photosynthesis and plant growth)
The increase in rates of photosynthesis under elevated CO2 levels increases diffusion of C02 from outside into the stomata increased C02 increases the concentration gradient increases the rate of photosynthesis
trend in average sea surface temperatures over the past 50 years
The upper ocean has warmed as a result of the increase in net energy, which is absorbed by surface waters more than 60% of net energy increase in the climate system is stored in the upper ocean, ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971-2010
Future predictions: general global trends in average temperature and precipitation
There will be general increases in average temperature and precipitation
Future sea-level rise - primary causes
Thermal expansion, melting of ice sheets (Greenland and Antarctica) and glaciers/ice caps
Climate change and sea-level rise Past 18,000 years
When ice cover was at its maximum at the end of the Ice Age, sea level was over 100 meters lower than it is today It increased steadily until the beginning of the inter-glacial period (glaciers melting)
Fate of carbon dioxide emissions - only a portion remaining in atmosphere.
carbon releases 85.5 gigatons carbon in the atmosphere: 49.9 gigatons missing 35.6 gigatons due to ocean uptake Only a portion remaining in atmosphere; most of it goes into terrestrial ecosystems
ocean flow as a result of greenhouse effect
currents have changed markedly, with a 30% decline in the southwards flow of deep cold water; northern oceans become less saline and less salinity means a lower density; the waters then cannot sink, so the conveyor weakens
Major factor(s) controlling the uptake of CO2 by the oceans?
diffusion
Potential influence of rising atmospheric concentrations of CO2 on greenhouse effect and global energy balance.
increase C02, everything redistributed (patterns of wind, circulation, evaporation, precipitation) energy balance is a function of exchanges of electromagnetic radiation (called wave length and quantity that is emitted, function of its temperature) sun emits shortwave radiation (solar radiation) earth (considerably cooler) emits less quantity of longwave radiation greenhouse effect: outgoing radiation absorbed by greenhouse gasses and reflected back to the surface direct effect on the net radiation and effect of the radiation balance longwave radiation goes back into the atmosphere, contributes to the layer of greenhouse gases Rising levels of CO2 in atmosphere have caused increases in greenhouses gases and increased greenhouse effect (more longwave radiation being trapped in atmosphere); this causes a surplus in net radiation
Leading contributors to rising atmospheric concentrations of CO2 as a result of: Burning of Fossil fuels Forest clearing/burning How have the above two factors functioned to change the global carbon cycle?
increased the C02 levels but there is missing C02 that has escaped the atmosphere 6-7 gigatons of carbon per year goes to the atmosphere through the burning of fossil fuels goes to the atmosphere 2 gigatons of carbon per year goes to the atmosphere through the clearing of forests (fast carbon cycle) We're also taking 6 gigatons per year from the fossil fuels in the earth and putting it back into the atmosphere quickly (taking the slow carbon cycle too)
CO2 and ocean acidification
increasing CO2 concentrations in upper levels of ocean water have resulted in decreased pH levels (more acidic) absorbed 30% of emitted anthropogenic carbon dioxide - causes ocean acidification
biomass enhancement ratio
ratio of biomass growth at elevated and ambient levels of CO2
