Chapter 8 Physical Geography
What is NOT an observed impact of climate change?
An increase in mountain glaciers and snow covers in both hemispheres.
Glacial Ice and Permafrost
As temperatures rise in Earth's atmosphere, glaciers are losing mass, shrinking in size in a process known as Glacial Retreat. ---The two largest ice sheets, in Greenland and Antarctica, are also losing mass. ---Summer melt on the Greenland ice sheet increased 30% from 1979 to 2006, with half the surface area of the ice sheet having some melting on average during the summer months. -Recent satellite studies show that portions of the West Antarctic Ice Sheet (WAIS) are in an irreversible decline, thinning, losing mass, and flowing more quickly toward the sea. --Permafrost is thawing in the Arctic at accelerating rates. ---Scientists now estimate that between 1/3 and 2/3 of Arctic permafrost will thaw over the next 200 years, if not sooner. ---Warming land and ocean temperatures may also cause the thaw of methane hydrates stored in permafrost and in deep-ocean sediments on the seafloor.
What is true about atmospheric Carbon dioxide concentrations?
CO2 concentrations surpassed 440 ppm in 2013, a level unprecedented during the last 800,000 years.
What is the most dominant gas in radiative forcing?
Carbon Dioxide
The use of tree rings to reconstruct past climates is known as
Dendroclimatology
The last time temperatures were similar to the present day interglacial period was during the
Eemian interglacial (about 125,000 years ago)
Sea Ice
Frozen seawater that forms over the ocean ---Melting sea ice does not contribute appreciably to sea-level rise because the ice almost displaces its own volume in seawater. ---Arctic Sea Ice, known as Pack Ice, is especially important for global climate owing to its effects on surface albedo. ---According to satellite data, Arctic summer sea ice reached its lowest extent in the modern record in 2012. ---Satellite data show that the summer sea-ice minimum extent and winter sea-ice maximum extent have declined since 1979. ----September sea ice is declining at a rate of 11% per decade ---Some scientists estimate an ice-free summer Arctic Ocean within the next few decades, which would accelerate warming and related changes to the global climate system.
Computerized models that characterize portions of the atmosphere and ocean in terms of climate-related variables are known as
General Circulation Models (GCMs)
The IPCC Fifth Amendment Report concludes that
Humans have been the dominant cause of the observed warming since the mid 20th century.
Methods for short-term climate reconstructions do not include
Ice Core Analysis
The graph plotting the ongoing changes in concentrations of carbon dioxide since 1958 is known as the
Keeling Curve
What is the legally binding international agreement that seeks to reduce emissions of greenhouse gases?
Kyoto Protocol
Sea-Level Rise
Mean Sea-Level=Elevation on Earth ; a value based on average tidal levels recorded hourly at a given site over many years. --Changes in sea level represent changes in the volume of water in the oceans, and these changes relate to temperature in the long-term. --The rate of rise in sea level along coastal Argentina is greater than the rate along coastal France. --The rate of rise along the US East Coast is greater than along the US West Coast. ---Roughly 2/3 of rise comes from the melting of land ice and 1/3 comes from the thermal expansion of sea-water that occurs as oceans absorb heat from the atmosphere and expand in volume.
What is two-thirds of observed sea level due to? One third?
Melting of Land Ice=2/3 Thermal Expansion=1/3
The second most prevalent greenhouse gas produced by human activity is
Methane (CH4)
Periodic changes in the Earth's eccentricity, axial precession (wobble), and obliquity (axial tilt) are known collectively as
Milankovich cycles
Per capita emissions of total greenhouse gases is highest in
More-developed countries (MDC)
What is true about the scientific consensus surrounding climate change?
Of actively publishing climate scientists, 97-98% support the conclusion that ongoing climate change is anthropogenic.
Both ice core and ocean sediment core use
Oxygen isotope analysis to reconstruct past climates.
Carbon Dioxide
Present concentration in Earth's atmosphere is higher than at any time in the last 800,000 years or longer --Began rising after Industrial Revolution ---Fossil-fuel burning, transportation, and heating accounts for 70% of CO2 emissions.
Temperature
Since 1880, the period from 2000 to 2010 was the warmest decade, with the years with the warmest land surface temperatures being 2005 and 2010 in the Northern Hemisphere. ---2009 was the warmest year in the Southern Hemisphere -The number of unusually hot days has been rising steadily in the US since 1900. ---2012 broke all US records since 1895 with average temperatures 55.3 degrees F --Sea-surface temperatures rose at average rate of 0.13 degrees F per year from 1901-2012 as oceans absorbed heat. ----This increasing heat content is consistent with sea-level rise from thermal expansion of seawater
What represents the largest active carbon sink?
The oceans
Methane
The second most prevalent greenhouse gas, with concentrations increasing from human activities. ---Atmospheric methane concentrations are increasing at a rate even faster than that of carbon dioxide. ---Has residence time of 12 years in the atmosphere, shorter than CO2 ---More efficient at trapping longwave radiation ---Largest sources are anthropogenic, accounting for about 2/3 of the total. ---Scientists suggest that it is released from permafrost areas and long continental shelves in the Arctic as methane hydrates thaw, potentially a significant source.
Nitrous Oxide
Third most important greenhouse gas produced by human activity --Increased 19% in atmospheric concentration since 1750 --Now higher than at any point in the last 10,000 years ---Residence time 120 years ---Recent rise attributed to emissions associated with agricultural activities.
What is the most abundant greenhouse gas in the Earth's atmosphere?
Water Vapor (H2O)
The primary anthropogenic source of carbon dioxide (CO2) is
the burning of fossil fuels
Contributions of greenhouse gases
--Increasing concentrations of greenhouse gases absorb longwave radiation, delaying losses of heat energy to space and resulting in a warming trend in the atmosphere. --Global warming causes complex changes in the lower atmosphere that drive the shifts in climate. ---Today, CO2 levels far exceed the natural range that has been the norm for hundreds of thousands of years. ---The contribution of such greenhouse gas toward warming the atmosphere depends on: which wavelengths of energy the gas absorbs ---the gas's residence time, and the length of time that it resides in the atmosphere Primary greenhouse gases in earth's atmosphere: 1) Water Vapor 2) Carbon dioxide 3) Methane 4) Nirtous Oxide 5) Halogenated gases --Water Vapor is the most abundant greenhouse gas, but has short residence time in the atmosphere ---Carbon Dioxide has a longer residence time because it remains in a gaseous state at a wider range of temperatures.
Causes of current climate change
-Rising concentrations of greenhouse gases in the atmosphere are the main cause of recent worldwide temperature increases. ---CO2 emissions associated with the burning of fossil fuels have risen with human population growth and rising standards of living. ---Scientists track the amount of carbon burned by humans over periods of years or decades by estimating the amount of CO2 released by different activities. ---Scientists have used carbon isotopes to more accurately determine the atmospheric CO2 emitted from fossil fuels. ---These data show that most of the CO2 increase comes from the burning of fossil fuels.
Three Key Elements of Climate Change Science
1) Study of Past climates 2) Measurement of current climatic changes 3) Modeling and projection of future climate scenarios
Since 1880, the two years with the highest land surface temperatures were
2005 and 2010
