Climate change: Impacts

HON 305VDr. Andersen

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

Glacial and interglacial periods during the Pleistocene

The current interglacial

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

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

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)

Each decade gets warmer

Remember the carbon dioxide measurements from Mauna Loa?

Connect the dots.

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)

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

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

Sea level rise in the 20th century

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

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

From IPCC AR-4 2007

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))

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)

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)

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)

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)

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)

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)

Observed climate change impacts on species are consistent with predicted impacts

1) PhenologyWalther et al 2002Parmesan & Yohe 2003Doswald et al 2009

2) Range shiftsParmesan et al 1999Parmesan & Yohe 2003Tingley et al 2009

3) Other effectsLaurance 2008Boersma et al 2009

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

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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, ClimateWizardOccurrence data: GBIF, Natural Heritage programs

2. Where will those conditions be found in the future?GCM predictions

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MaxEnt provides parsimonious estimation of bioclimatic envelopes

Machine learning algorithm to estimate geographic distributions under current and future conditions

Phillips et al 2006Baldwin & Bender 2007Phillips & Dudik 2008

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Bioclimatic models predict habitat loss in the American Pika (Ochotona princeps)

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Regional losses of 53% to 71% across 5 regions

(Calkins MS thesis, NMSU, 2010)

Bioclimatic models predict patterns of habitat loss in European bats

lNorthern species more likely to suffer losses than temperate and Mediterranean speciesRebelo et al 2010

A mixed approach predicts species distributions based on the distributions of habitats

1. Use MaxEnt to predict future distributions of habitat typesRelies on Gap Analysis Project landcover data

2. Overlay existing deductive animal distribution models on future habitat distributionsRelies on Gap Analysis Project animal distribution models

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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 temperaturesRedman et al MS

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)

● 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?