Hallie Young
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Global temperature measurements: since when do they exist,
weve been measuring (from a bit above the gorund) since arounf 1880
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how are they averaged globally?
taking the temperatures from around the world and averagine them out with appropriate weight (like for the amount of land mass etc) using actual measutements thermometers
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Why are temperature anomaly records used, rather than absolute temperature values?
use average of century as a base (for example 1901-2000)
thats a base of a century
better way to see the deviation from averrage and to compare more accurately the variability of the temperature rather than the absolute temperature
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What should be the minimum number of years used as a base period?
30 years are usual base, 100 years sometimes used
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• By how much has global temperature increased over the last century?
lately the deviation from norm has been almost 1 degree celcius, but overtime the difference between largest and smallest deviations have been about 1.4 degrees celcius
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Which areas have heated up the most (and why)?
ARCTIC- northern hemisphere
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cryosphere
all the frozen parts of earth system
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Antarctic Ice sheet area (percent of surface of earth) and mass
2.7% of earth
53 units (10^3 kg/m^2)
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recent trends in arctic sea ice extent, thickness, volume?
sea ice minimum has been on a severe downward trend, younger and thinner ice that wont survive melting. multiyear ice volume trend downward
arctic snow cover dropping
until 1970, sea ice was relatively constant
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what is sea ice minimum
sea ice is measured using satellites emaning we cant literally measure every single bit of ice/be completely 100% sure of the ice.
the minimum is the minimum possible amount of ice that exists as indicated by the data (satellite image pixels. nasa says they use pixels at least 15% covered in ice as the base)
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what is permafrost
permafrost is frozen ice inside of the earth/ground
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why is arctic heating more than antarctic
lack of continent in north pole, arctic ocean
more qater=ice albedo the swa ice melts eeasilyy
south has more land and glacial sheets and higher albedo
arctic has warmed in 2-3 more than rest of earth based on temp anomaly
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By how much would global sea level approximately change if the Greenland Ice Sheet melted?
about 7m increase in sea level
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Why might collapsing ice shelves accelerate ice sheet decline?
change ice flow
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permafrost melt
lower albedo
exacerbate problem
bacteria trapped inside
release methane
bacteria decay release co2
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By how much would global sea level approximately change if all of the Antarctic ice melted?
60
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By how much would global sea level approximately change if all of the Antarctic ice melted?
6
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Why might collapsing ice shelves accelerate ice sheet decline?
they can melt into water thus accelerating the icea albedo
melt and become part of ice streams which will break off more ice sheets/lubricate ice sheets into breaking off
when they enter these ice streams, increasing currents (also heat increases this speed)
exposes more areas of the shelf to rapid currents
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What is permafrost? How does its melting influence the climate system?
frozen water inside the ground
(soil with temp @ or below freexing)
typically covered in snow
releases bacteria when melting that release methane into atmosphere when decay
also less snow on top = lower albedo
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By how much has global sea level risen over the last century?
25 cm ish
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How is the global sea level being monitored?
sattelites
ground measurements (tide gauges) (but sinkinh or rising land etc could affect results)
measure sirface temp, currents, speed, ocean color
argo system: dives and goes down and up, floats where the ocean current takes them
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What has been the rate of sea level rise during the past 2-3 decades? What are the major causes for this rise?
sea level rise is now exponentially increasing
3.4 mm/year
melting ice/added water (sea ice doesn't affect this because it's already in the ocean/mass is already there)
thermal expansion (warm water expands, more mass than cold water)
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Observed trends over the past decades in ocean heat content, heat waves, precipitation extremes and distribution
ocean heat: increasing steadily
heat waves (no exact spec. def): more frequent, intenser, longer, season length increase
precipitation: wetter in wet areas (east, extreme northwest) and drier in dry areas (west). warmer atmospheres hold more water vapor and are more chaotic/fast
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How has hurricane intensity changed in recent decades, and what is the likely cause for this change?
hurricane numbers haven't changed
hurricane intensity, duration, and size have increased
warm climate: faster moving, more turbulent, more water vapor
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Recent trends in Arctic sea ice extent, thickness, volume
THINNNER
YOUNGER
SHRINKING EXTENT
