Lecture 8 Flashcards
The recession of sea ice is proceeding so quickly that an ice-free summer by 20__ – 20__ is not unlikely
2030-2050
Weather vs. Climate
Weather refers to meteorological conditions at the moment, including properties normally associated with a weather forecast — temperature, humidity, wind speed and atmospheric pressure.
Climate refers to average weather conditions, typically over a period of 30 years.
The definition of time scale for abrupt climate change is
The definition of time scale for abrupt climate change has shifted from centuries in the 1970s to decades as new evidence of rapid shifts in Greenland’s climate was revealed from ice cores.
-In addition, the shift of Alaskan temperatures concurrent with a phase change of the Pacific Decadal Oscillation (PDO) is now considered to be an example of abrupt climate change (Figure 8-15). Abrupt climate change is very important for inhabitants of Earth since it may not always be possible to adapt quickly enough to avoid harm or extinction. It has been argued that the development of agricultural societies needed the relatively stable climate that has been present during the past 2000 years (Feynman and Ruzmaikin, 2007).
Young Dryas event
-described what happened?
Younger Dryas (Figure 8-5), which was a worldwide cooling event between about 12,900 and 11,600 years ago as the Earth was moving from a glacial to interglacial state. Ice core evidence from Greenland collected in the late 1980s provided evidence of a gradual cooling starting about 12,900 years ago followed by an abrupt reversal and sharp warming at the end of the Younger Dryas 11,600 years ago (Alley, 2000).
As Arctic sea ice melts and fresh water is transported into the North Atlantic, a stable surface layer forms in the ocean reducing deep-water formation. The Meridional Overturning Circulation (MOC) is synonymous with the thermohaline circulation (Figure 8-6) and describes a global circulation loop with sinking motion at high latitudes, southward motion of cool water at depth and northward motion at the ocean surface. This leads to a slow down of the MOC reducing poleward heat transport and leading to cooling in the North Atlantic sector.
thermohaline circulation:
a global ocean circulation that is driven by density gradients resulting from changes in temperature and salinity.
Forcing factors
are phenomena that influence the Earth’s energy budget and climate; they can be associated with natural variability and anthropogenic climate change
The Arctic and the North Atlantic are connected through the ______ and the ________.
Explain
The Arctic and the North Atlantic are connected through the atmosphere and the ocean. The atmosphere transports energy from lower latitudes poleward in the form of sensible and latent heat through circulation patterns. The ocean also transports heat poleward with the vast majority entering the Arctic through the North Atlantic. Warm salty water enters the Arctic from the North Atlantic Ocean surface and plunges below the cooler, less salty and lower lighter-density Arctic Ocean to form the Atlantic Water layer. This water transports large amounts of heat into the Arctic, the fate of which is an active area of research since it could warm the upper ocean layer and lead to ice melt from below (Polyakov et al., 2005). The ocean with its large heat capacity changes slowly compared to the atmosphere and thereby moderates the climate.
Sunspot activity
Decreased sunspot activity is linked with lower solar radiation promoting cooling, whereas increased sunspot activity is linked with higher solar radiation promoting warming. Feedbacks in the climate system can magnify the impact of the changes in solar irradiance.
precession of the equinoxes
The elliptical shape of the Earth’s orbit rotates moving the long and short axes of the ellipse. Together the wobble and turning of the ellipse are called the precession of the equinoxes at a frequency of 23,000 years
Humans have impacted the energy balance of the _______ by changing the…
Humans have impacted the energy balance of the atmosphere by changing the atmospheric composition of greenhouse gases, which capture long-wave radiation released from the Earth’s surface. Carbon dioxide (CO2), which has increased in the atmosphere largely due to fossil fuel combustion, has had the greatest effect on the Earth’s energy balance and climate.
To attribute Earth’s warming to particular causes, scientists carry out “_______ studies” in which data for climate variables (e.g., global mean surface temperature, radiation losses to space, temperature profiles through the atmosphere) are compared with expected natural and anthropogenic forcing factors, including solar radiation, greenhouse gases and aerosols
fingerprint
Humans are the cause of __ percent of the higher net radiative forcing (promoting warming) in 2005 compared to 1750 based on forcing factors alone.
94
Greenhous Gas Effects on climate change
Multiple lines of evidence indicate that Earth’s energy imbalance is due primarily to the rise in anthropogenic greenhouse gases. Due to higher concentrations of greenhouse gases (primarily carbon dioxide and methane) the energy and heat content of the troposphere (the lower part of the atmosphere where weather takes place) is increasing; as that heat is radiated, it warms the oceans and air above the Earth’s surface. Importantly, the greenhouse gas effect is direct and indirect. It is direct through absorption of long-wave radiation and indirect through the increase in atmospheric water vapor (also a greenhouse gas) that results from CO2-induced warming (Lacis et al., 2010). Changes in climate properties are consistent with warming due to anthropogenic greenhouse gases.
Greenhous Gas Effects on climate change
Multiple lines of evidence indicate that Earth’s energy imbalance is due primarily to the rise in anthropogenic greenhouse gases. Due to higher concentrations of greenhouse gases (primarily carbon dioxide and methane) the energy and heat content of the troposphere (the lower part of the atmosphere where weather takes place) is increasing; as that heat is radiated, it warms the oceans and air above the Earth’s surface. Importantly, the greenhouse gas effect is direct and indirect. It is direct through absorption of long-wave radiation and indirect through the increase in atmospheric water vapor (also a greenhouse gas) that results from CO2-induced warming (Lacis et al., 2010). Changes in climate properties are consistent with warming due to anthropogenic greenhouse gases.
- providing evidence that the Earth is losing less heat to space because higher greenhouse gas concentrations are increasing heat retention in the troposphere.
- In summary, most analyses of satellite data to date indicate that Earth is receiving more energy than it is releasing into space. The range may be a few W m-2 but is more likely in the range of 1 W m-2. The findings from the satellite data are consistent with climate models that incorporate known forcing factors. More accurately and precisely determining Earth’s energy balance from direct measurements is beyond the technical capabilities of current satellites.
Cloud and Earth Radiant Earth System (CERES)
Satellites, starting with the Nimbus satellites, have been measuring incoming solar radiation and outgoing longwave radiation since the 1970s. Currently those measurements are being made by the Cloud and Earth Radiant Earth System (CERES) instrument aboard three NASA satellites
Air temperatures in the stratosphere (10 – 50 km above Earth’s surface), which have been measured by weather balloons, satellites and other instruments for the past two to three decades, show a ______ trend…
cooling
consistent with the trapping of longwave radiation by greenhouse gases in the lower troposphere and the depletion of the stratospheric ozone layer
- Less long-wave radiation reaches the upper troposphere and stratosphere because elevated greenhouse gases in the lower troposphere capture long-wave radiation released from Earth’s surface.
- Ozone depletion is another cause of stratospheric cooling. Ozone absorbs ultra-violet (short-wave) radiation from the Sun resulting in heat radiation. Cooling resulted because ozone declined in the mid-to-late 20th century due to the use of chlorofluorocarbons for cooling and industrial uses. Volcanic eruptions, which have a short-term effect on air temperature, caused warming of the stratosphere but cooling of surface air.
surface and stratosphere have opposite relationship
Name 4 anthropogenic forcing factors
Forcing factors used to drive global climate models include greenhouse gases, solar irradiance, aerosols (anthropogenic and volcanic) and land and cloud albedo (reflectivity)
Emissions scenarios, which were developed by over 50 specialists spanning a range of disciplines (including economists, social scientists and geoscientists) and from 18 countries, are based on 4 different storylines based on 3 variables
demographic development, socio-economic development and technological change.
The IPCC in 2007 released climate-model projections for global 21st century climate based on the SRES (greenhouse gas emissions scenarios). The models forecast a mean global temperature rise of about ___ degrees C per decade for the next two decades and varying rates of continued warming through the 21st century for the different scenarios.
Warming over the 21st century is forecast to range from ___ degrees C if atmospheric CO2 remains at year 2000 levels to ___ degrees C for the A1F1 scenario that assumes rapid economic growth, a global population that peaks mid-century and continued high reliance on fossil fuels.
- 2
- 6
- 0
- Increases in the Arctic are roughly twice the global average and range from roughly 4oC to 7.5oC
Warming is forecast to be _____ over land than oceans and _____ at high latitudes
greater
greatest
Transpiration in climate change
Transpiration (i.e., water vapour released by plants during photosynthesis) and evaporation increase with temperature and warm air holds more water vapour than cold air, a warmer world on average will therefore be wetter (Figure 8-31). An increase in transpiration and evaporation means global precipitation will increase. Spatial variability will be critically important and spatial differences in precipitation will be more pronounced than those for temperature. Large areas of the subtropics (already very dry) will be drier while the deep tropics and the mid-to-high latitudes (temperate zone, boreal zone and polar regions) will be wetter. The polar regions and deep tropics will experience the greatest increase in precipitation. Precipitation in the Arctic is forecast to rise as much as 20 percent (compared to 1980 – 1999) by 2100 for the mid-range A1B scenario with most of the increase in the winter.
Describe the general climate change pattern predicted for the Arctic nations in terms of patterns of precipitation and warming
Most regional models for Arctic regions and the eight Arctic nations show the same patterns as those forecast by the global models for high latitudes — amplified warming, concentrated in the winter and fall, and higher annual precipitation largely concentrated
in the winter — but with finer spatial variability. Forecast changes have greatest spatial variability in areas with complex topography, particularly mountainous regions, and warming tends to be most elevated farther from the coast where ocean and currents moderate air temperature changes
Define Vulnerability, Resilience, and Adaptive Capacity
Vulnerability is susceptibility to be harmed.
Resilience is the capacity for a system to return to predisturbance or near pre-disturbance conditions without loss of essential character and function after a disturbance or application of new impacts or pressures.
Adaptive capacity is the capacity of a system to adapt to impacts, pressures or disturbances without harm and potential benefit.
IPCC did not include increases in the dynamics of the Greenland and Antarctic ice sheets in the models used to calculate future sea level (Archer and Rahmstorf, 2010), but projected sea level to rise __ – __ cm (relative to the 1980 – 1999 mean) by 2090 – 2099
18-59
Since satellites began measuring ice extent in 1979, the extent of September ice (the annual minimum) has declined by about __ percent overall, an astonishing rate of __ percent per decade
30
11
- More Arctic ice is made up of new first year ice (i.e., thinner) instead of multi-year ice (i.e., thicker) (Figure 8-44). Since the ice is thinner, its potential for melting is higher and it is more likely to be broken up and moved by winds and ocean currents out of the Arctic basin.
Arctic sea ice decline is caused by either or both of two factors:
- increased melting due to higher surface air and water temperatures, including a longer melt season,
- increased transport of ice out of the Arctic basin through the Fram Strait between Svalbard and Greenland.
Should or when the Arctic become ice free in the summer it will be the first time in at least ______ years
800,000
At the global scale approximately __-__ percent of species assessed to date are at increased risk of extinction if global mean air temperature rises by 1.5 – 2.5oC
20-30%
How will climate change affect primary production in the worlds oceans
There is still disagreement about how climate warming will influence primary production. The growing consensus is that primary production for the world’s oceans will decline because higher ocean temperatures will increase vertical stratification and decrease upwelling of nutrients from deeper waters to surface waters that contain phytoplankton
Agriculture and Climate change
Agricultural productivity is predicted to increase at the global scale, decrease in the subtropics and increase at higher latitudes up to a warming of roughly 1 – 3oC (Anisimov et al., 2007; Easterly et al., 2007; IPCC, 2007; Gornall et al., 2010; Henson, 2011; Smith, 2010). Higher yields especially for cereal crops are anticipated at higher latitudes due to higher summer temperatures and a longer growing season. The northern margin of agriculture will be extended by potentially several hundred kilometers over this century
- Plant health and yields at mid to high latitudes are predicted to decline with warming greater than 2 – 3oC
- Agriculture at northern latitudes and among Arctic nations should benefit from climate change at least during this century.
Forestry and Climate Change
At the global scale, higher atmospheric carbon dioxide and longer seasons generally are forecast to promote commercial forest productivity at a modest level with increases shifting from lower latitudes in the short-term to higher latitudes in the long-term
(Easterling et al., 2007). Another positive factor will be the range extension of the boreal forest into tundra and potentially northward extension of tree plantations. Forest fire frequency is forecasted to increase, forest pests will extend their range northward and some areas will experience droughts as increased evapotranspiration (i.e., water losses) due to higher temperatures outweighs increased precipitation. The southern portion of the boreal forest is projected to be converted to an open forest-steppe community due to greater water deficits (Flannigan et al., 2005; Juday et al., 2005). How the potential yield of harvestable timber and pulpwood will respond to climate change cannot be forecasted with confidence because of uncertainties of climate forecasts, particularly at local to regional levels. The amount of warming and plant water availability will remain controlling factors. As with fisheries and agriculture, timber production response will depend largely on the capability and adaptive capacity of the forestry industry together with fire management practices.
DO YOU KNOW THESEEEEE
Abrupt Climate Change: Aerosols: Albedo: Climate: Climate Change: Climate Variability: Earth’s Orbital Cycles: Energy Balance: Feedback Loops: Greenhouse Gases: Proxy Data: Radiative Forcing Factor: Reflectivity: Residence Time: Specific Heat: Weather:
Abrupt Climate Change: Climate change that is happening very quickly, over decades rather than centuries, with rapid shifts in temperatures.
Aerosols: A gaseous suspension of fine solid or liquid particles.
Albedo: The degree to which a surface reflects light.
Climate: The meteorological conditions, including temperature, precipitation, and wind, that characteristically prevail in a particular region.
Climate Change: A departure from normal weather conditions (30-year average).
Climate Variability: An increase in extreme highs and extreme lows.
Earth’s Orbital Cycles: Variations in the Earth’s tilt, the pattern that the Earth circumscribes around the Sun, and the direction of the Earth’s north-south axis that influence the distribution of solar radiation by latitude.
Energy Balance: The arithmetic balancing of energy inputs versus outputs for an object, reactor, or other processing.
Feedback Loops: A system that allows for feedback and self-correction and that adjusts its operation according to differences.
Greenhouse Gases: Atmospheric gases that trap long wave radiation (heat) released from the Earth’s surface, occur naturally and are released due to human activity.
Proxy Data: Data such as tree rings and isotope concentrations in ice cores that are used to infer temperatures for periods that pre-date the period when thermometer measurements were made.
Radiative Forcing Factor: A factor that promotes climate warming or cooling.
Reflectivity: the fraction of radiant energy that is reflected from a surface.
Residence Time: the duration of persistence of a mass or substance in a medium or place (such as the atmosphere).
Specific Heat: The heat required to raise the temperature of one gram of a substance one degree centigrade.
Weather: The state of the atmosphere at a given time and place, with respect to variables such as temperature, moisture, wind velocity, and barometric pressure.
