Climate change is already causing impacts such as rising global temperatures, sea level rise, and more extreme weather events. Many models predict these changes will intensify in the coming decades and severely impact natural systems and human communities through increased wildfires, shifting agricultural patterns, and displacement from rising seas. Understanding past climate shifts and carefully planning adaptation and mitigation can help minimize harm from the ongoing and inevitable impacts of climate change.

1. Climate change: Impacts
HON 305V
Dr. Andersen

2. How does current climate change compare
to climate change in the geologic past?
● Sources of data on past climates
● Tree rings
● Glacial ice (and trapped air bubbles)
● Ocean sediments
● Coral reefs
● Current climate change much more rapid than
anything seen in paleoclimate reconstructions

3. Glacial and interglacial periods
during the Pleistocene

4. The current interglacial

5. Example: the PETM
● PETM = Paleocene-Eocene Thermal Maximum
● About 50 million years ago
● During the Cenozoic
● About 10 million years after the dinosaurs went extinct
● Crocodiles and palm trees north of the Arctic Circle
● Temps on U.S. Gulf Coast averaged 80 degrees F (5
degrees hotter than currently), and varied about 9
degrees F across seasons (vary about 21 degrees
across seasons currently)
● Ocean temperatures increased by 5 to 7 degrees C in
about 10,000 years

6. The PETM, II
● Apparently coincided with a global “burp” of
carbon release equivalent to burning the rest of
Earth's known fossil fuel reserves
● Possible that mild warming led to release of
methane hydrates on ocean floor into the
atmosphere
● Current rate of release of carbon into the
atmosphere is about 10 times higher than
during the PETM

7. How is the climate already
changing?
● About 15,000 high-temperature records were
broken during March 2012
● As of 2010, the 15 warmest years on record
since 1880 had all occurred within the previous
16 years
● Global average temperatures have risen about
0.7 degrees C since 1957 (a very good year)

8. Each decade gets warmer
Remember the
carbon dioxide
measurements from
Mauna Loa?
Connect the dots.

9. What impacts of climate change are already being seen?
Some eastern North American
tree species migrating northward
1 km per year.
(Woodall et al 2009)
Around James Bay in Canada,
the permafrost line has receded
130 km in the last 50 years.
(Payette & Huppe 2010)

10. How much can we expect temperatures to
rise through the end of this century?
● Current IPCC projections are for 2 – 11 degrees
F increase in global average
● Regional changes may be less or greater
● Temperature increases for the U.S. Expected to
be about 30% higher than average
● The Arctic is expected to warm up the most,
and is already warming at twice the global
average rate

11. What about sea levels?
● Not rising because of melting sea ice,
but continental ice (Greenland and
Antarctica – above sea level)
● Sea level could rise by 1.5 to 6 feet by
the end of the century
● Bangladesh will lose 17.5% of its land
area if sea level rises 3 feet
● The Maldives and other island chains
may disappear completely

12. th
Sea level rise in the 20 century

13. Impacts on precipitation
● Higher temperatures → more evaporation
● Faster hydrologic cycle
● More rainfall in some places, less in others
● In general, less rain on either side of the equator, more
in high latitudes
● Less snow in the mountain West will impact
● Fish populations
● Hydropower
● Recreation
● Municipal and agricultural water availability

14. Hydrology
● Altered annual streamflows
● Changes in timing of runoff
● Changes in relative length of low-flow and high-flow conditions
● Different watersheds differentially vulnerable
(Null et al. 2010, PloS ONE 5(4))
● Current reservoirs, canals etc. built for current
conditions, not future conditions

15. From IPCC AR-4 2007

16. Wildfire regimes will change
● 10% to 50% increase in fire activity across
North America by 2050
● Effects of fire on vegetation may overshadow direct
effects of climate change on distribution,
abundance, and dispersal
(Flannigan et al., 2000, Science of the Total Environment, 262:221-229)
● Increases in fire frequency in some regions
may be balanced out by decrease in others
● Still, expect substantial change in global fire
regimes
(Krawchuk et al., 2009, PloS ONE 4(4))

17. Changing fire regimes will impact
society
● Increases in
● Fuel load
● Ignition rate
● Fire intensity
● Length of fire season
● May overwhelm agency fire response and
suppression capabilities
(Podur & Wotton, 2010, Ecol. Modell. 221(9): 1301-1309)

18. Potential for crop failures
● Agriculture throughout Africa runs some risk of
negative impacts from climate change
● Existing cropping systems and infrastructure not
sufficient to meet current demand
(Muller et al., 2011, Proc. Nat. Acad. Sci., 108(11):4313-4315)
● Regions with highest food insecurity (South
Asia and Southern Africa) face greatest risk of
reduced yield and crop failure
(Lobell et al., 2008, Science 319(5863):607-610)

19. Mechanisms and severity of crop
failures
● Simulation studies of spring wheat in
northeastern China
● Increased crop failure rates under future climate
– Thermal stress
– Water stress
● Maximum failure rates increase more rapidly
than median failure rates
(Challinor et al., 2010, Env. Res. Lett. 5(3): 034012)

20. Mitigating crop failures
● Farmers can protect themselves from some of
the effects of climate change by planting a
more diverse array of crops
(Lin, 2011, BioScience 61(3):183-193)
● Even crops thought to be heat-tolerant may be
more sensitive to rising temperature than we
expect
● 1C temp. increase → yield loss in 65% of African
maize-growing region
(Lobell et al., 2011, Nature Climate Change, doi:10.1038/nclimate1043)

21. The impacts are not limited to land-
based food production
● Impacts on anadromous fish
● Warmer temperatures
● Earlier peak stream flow
(Martins et al., 2011, Global Change Biology, 17(1):99-114)
● Impacts on marine fisheries
● Temperature
● Salinity changes (particularly in coastal fisheries
with nearshore/estuarine spawning)
(Lindegren et al., 2010, Proc. Roy Soc. B 277(1691):2121-2130)
(Hare et al., 2010, Ecol. Appl. 20(2):452-464)

22. Climate change impacts on ecosystems
● The growing season in parts of the Northern
Hemisphere became two weeks longer in the
second half of the 20th century
● Spring is coming earlier in both hemispheres
● Longer growing seasons impact
● Pollinators
● Migratory birds
● Pests (also influenced by milder winters)
● Water availability (more evaporation and transpiration)

23. Observed climate change impacts on species are
consistent with predicted impacts
1) Phenology
Walther et al 2002
Parmesan & Yohe 2003
Doswald et al 2009
2) Range shifts
Parmesan et al 1999
Parmesan & Yohe 2003
Tingley et al 2009
3) Other effects
Laurance 2008
Boersma et al 2009

24. We can model the way in which current (and
future) geographic ranges depend on climate
+ = ?
1. Bioclimatic envelope models based on
Maximum Entropy (MaxEnt) criteria
2. Habitat-based approach

25. Bioclimatic envelope models combine the
answers to two simple questions
1. What are the climatic conditions in which a species is
currently found?
Climate data: PRISM, WorldClim, ClimateWizard
Occurrence data: GBIF, Natural Heritage programs
2. Where will those conditions be found in the future?
GCM predictions
+ = ?

26. MaxEnt provides parsimonious estimation of
bioclimatic envelopes
Machine learning algorithm to estimate geographic
distributions under current and future conditions
Phillips et al 2006
Baldwin & Bender 2007
Phillips & Dudik 2008
+ = ?

27. Bioclimatic models predict habitat loss in the
American Pika (Ochotona princeps)
l
Regional losses of 53% to 71%
across 5 regions
(Calkins MS thesis, NMSU, 2010)

28. Bioclimatic models predict patterns of habitat
loss in European bats
l
Northern species more
likely to suffer losses than
temperate and
Mediterranean species
Rebelo et al 2010

29. A mixed approach predicts species distributions
based on the distributions of habitats
1. Use MaxEnt to predict future distributions of
habitat types
Relies on Gap Analysis Project landcover data
2. Overlay existing deductive animal distribution
models on future habitat distributions
Relies on Gap Analysis Project animal distribution models
+ + =
?

30. Mixed approach predicts complex habitat loss
pattern for swift fox (Vulpes velox)
Complex response of grassland
habitats to future climate scenarios.
C3 grasses have advantage
at elevated CO2
C4 grasses prefer warmer
temperatures
Redman et al MS

31. Climate change threats to
biodiversity
● Globally, 15% - 37% of
species “committed to
extinction” due to climate
change alone, not including
effects of other factors
(Thomas et al 2004, Nature 427:145 – 148)
● Effects of climate change on
biodiversity by year 2100
likely to be exceeded only
by effects of land-use
changes
(Sala et al . 2000, Science 287:1770-1774)

32. ● How do predictions of future precipitation
distributions match up with what we know about
global patterns of atmospheric circulation
(Hadley cells etc.)
● How do paleoclimate studies help us to
understand and prepare for future climate
change?
● How might rising sea levels influence patterns
of human immigration?
● How might some of these impacts interact in
unexpected ways?