Lecture 11: Climate Change Part 2

Question 1

Phenology

Answer 1

• Study of cyclic and seasonal natural phenomena
• Integrates effects of temperature into their effects on organisms
• Examples:
  
  • Ice thaw in Canadian lakes
  • Bud burst in European trees
  • Date of first flower in British wildflowers
  • Flowering on spanish mountains
  • Changes in flowering overlap

Question 2

Bud burst in European Birch and Oak

Answer 2

• Budburst coming earlier between 1984-1999
• Budburst is emergence of new leaves or stems at start of the growing season

Question 3

Canadian lakes thawing earlier

Answer 3

• Spring comes sooner

Question 4

Cause of warming: Greenhouse effects or increased solar activity

Answer 4

• Poles warming faster than mid latitudes : Consistent with both solar and greenhouse
• Winter temps rising faster than summer: Consistent with both solar and greenhouse
• Nighttime temps rising faster than daytime: Not consistent with solar, but consistent with greenhouse
• Troposphere heating, stratosphere cooling : Not consistent with solar but consistent with greenhouse

Question 5

Human influence has warmed climate

Answer 5

• Observed changes similar to simulated human and natural factors

Question 6

Conclusions from skeptics

Answer 6

• Rebuilt global climate histories from scratch
• Created simple models based on CO2 concentration, volcanic eruptions
• Tested and rejected the effects of variation in solar radiation
• Soot keeps sun radiation from reaching earth surface, sets back global warming 2-3 years

Question 7

Global warming 1850 to 2024

Answer 7

• 2C by 2059
• 1.5C by 2033

Question 8

Places that are colder than they were before

Answer 8

• Greenland

Question 9

Predicted effects on human health

Answer 9

• Malaria: contraction and expansion, changes in transmission season
• Increase in malnutrition
• Increase in number of people suffering from deaths, disease, and injuries from extreme weather events
• Increase in frequency of cardio-respiratory diseases from changes in air quality
• Change in range of infectious disease vectors
• Reduction of cold related deaths
• Increase in burden of diarrheal diseases

Question 10

Consequences of various temperature increases

Answer 10

• Water: Increased water availability in moist tropics and high latitudes, decreasing water availability and increasing drought in mid latitudes and semi and low latitudes
• Ecosystems: Increasing amphibian extinction, increase in coral bleaching
• Food: In low latitudes, crop productivity decreases for some cereals. In mid-high latitudes, crop productivity increases for some cereals
• Coast: Increased damage from floods and storms
• Health: Increasing burden from malnutrition, diarrheal, cardio-respiratory disease
• Singular events: Local retreat of ice in greenland and west antartica

Question 11

Predictions, limitations, alternatives

Answer 11

• Weather events become more extreme because atmospheric heat engine more powerful
• Limitations: Modeling clouds difficult, coupling of land-ocean atmospheres weak, GCMs can’t yet make fine-scale regional forecasts
• Another approach: look at past warming cycles

Question 12

What were past extremes like

Answer 12

• Paleocene-Eocene Thermal Maximum (PETM) about 56 MYA
• Sudden spike in temperature and CO2 in an Earth that was already much hotter than now
• Rise of 6C over 20,000 years
• Warm period lasted 170,000 years
• Probably triggered by some positive feedback, most likely melting of frozen methane clathrates from the ocean

Question 13

Some PETM events

Answer 13

• Mass extinctions of oceanic foraminifera
• Ocean acidified from CO2, animals couldn’t make carbonate shells
• Migration of species and biomes
• Dwarfing of mammals
• Leaves shrank; more insect herbivory (damage to fossilized leaves)