Transcript Climate, Global Warming, and recent controversies

Global Climate Change - Evidence and Effects
One of the concerns facing humanity is our effect on
climates, due largely to our combustion of fossil fuels.
Scientists project increase in the global average
temperature of ~2º- ~10ºC, but important differences
across latitude and individual continents and lots of
variation among models.
3.7K (left)
and
precipitation
(right),
Based on
Current
CO2 levels
10.5K and
predipitation
based on a
doubling of
CO2
Why do they project increased temperature? Is there
historical evidence that leads to these projections?
How do projections differ among latitudinal zones?
If the projections are accurate, the effects on species
diversity, the patterns of species' distributions,
agricultural production, and sea level will by vast.
The Evidence:
1. The Historical Evidence –
Gases trapped in glacial ice tell us what atmospheres
were like in the past. Cores have been taken on
Greenland and in the Antarctic. The Vostok core
(Russian Antarcitica) is the major source for this
figure…
Wisconsin
glaciation
We have various sources to estimate climate over a
much longer span, at least 55-60 MY.
During Pleistocene glaciation, temperatures were
cooler than today, but this figure does not show
recent warming very well.
More recent increases in CO2 are better documented
with data from the Mauna Loa observatory in
Hawaii, well isolated from major industrial sources,
and therefore a good indicator of global pattern.
If we look at data from Mauna Loa in greater detail,
the seasonal cycle is evident. In winter in the northern
hemisphere, photosynthesis is reduced, but not
atmospheric input of CO2.
Recent increase looks approximately exponential.
Global climate and CO2 have changed in the past
naturally. How do we know we are responsible for
the recent increase?
1) The exponential increase over the last 150 years
has three "breaks". Those breaks match with the
First and Second World Wars and the Great
Depression. They are the three breaks in global
economic activity.
2) Isotopic ratios between C12 and C14 indicate fossil
fuel combustion is the source of increasing CO2
concentration.
The half life of C14 is 5,730 years. It decays into N14
by conversion of a neutron into a proton. C14 is formed
by the reverse conversion in the atmosphere when a
thermal neutron displaces a proton as a result of
cosmic radiation in the upper atmosphere. The rate of
C14 formation is essentially constant.
Living plants and animals take up C14 and C12 with
little selectivity (though there is selectivity against C13,
particularly in C3 plants).
Fossil fuels were formed millions of years ago. C14 in
them will have decayed after hundreds of half-lives.
What we find is an enormous depletion of C14 relative
to C12 in fuels compared to living plants.
If increasing carbon dioxide in the atmosphere is due
to fossil fuel combustion, rather than some sort of
natural change in current source-sink relationships,
then the isotopic ratio should have changed over time
due to the release of carbon with an enormously
reduced C14 content. The reduced ratio is called the
Suess effect. It is clearly evident.
from Baxter and
Walton (1970)
What are the predicted biological impacts of the
changes associated with global warming, and are
some of these changes already apparent?
Hughes (2000) argued that changes are evident, and
presented some of the patterns evident and expected
from global warming.
1.Plant growth physiology changes in increased CO2
atmospheres. Generally, growth rates increase, and
warming lengthens the growing season for plants.
The density of stomates decreases in many species,
since fewer openings are necessary to take in
sufficient CO2.
2. Species distributions change. Population sizes of
native vascular plants on Antarctica have increased
dramatically (by ~25x) from 1964-1990. Treelines
have moved upward along mountain slopes since
the turn of the 20th century. The ranges of nonmigratory European butterflies have generally
shifted northward by 35-240 kilometers (22 of 35
species, only 2 shifted southward).
3. The malaria plasmodium and its mosquito vector
now occur at higher elevations in Asia, Central
America, and Latin America. Dengue fever,
previously limited to 1000m elevation, reached
1700m in Mexico and 2200m in Colombia.
4. Birds have similarly extended their distributions
northward. In Britain, 59 bird species from the
southern portion had extended distributions
northward by an average of 19 km over 20 years
(1968-72 compared with 1988-91).
5. Life cycles and the timing of critical seasonal
events have changed. Egg laying in insects and
birds, flowering and seed set in plants typically
occur days earlier. Development may occur more
rapidly, particularly in insects. Initial flight in
holometabolous species (e.g. Lepidoptera) may
occur earlier.
Let’s look at some of these changes and their impacts
on conservation in greater detail.
Just in case you think all the global warming
evidence suggests uniform warming and changes
that might lead to to expect, we’ll first consider the
sea ice conditions in the regions where narwhals
overwinter.
The predictions are that arctic ice will be reduced in
extent and thickness on average, opening sea lanes
above Canada and Russia. That has not been the case
in the wintering grounds of the narwhal in Baffin
Bay (Laidre and Heide-Jorgenson, 2005). Instead,
the amount of open water required for narwhal to
breathe has been declining in recent decades.
March sea ice in Baffin Bay –
NWG is the narwhal’s northern
wintering ground, and SWG the
southern wintering ground.
How has the extent of sea ice
changed over recent decades?
Fraction of
open water
variability
Narwhal arrive at the wintering grounds when there
is around 60% open water. Then freeze up limits
their movements. They nevertheless show great site
fidelity.
Increasing sea ice in the wintering grounds probably
affects their feeding. They cannot move away from
open leads where they breathe. Increasing sea ice,
increased Greenlandic fishing for their main winter
food (Greenland halibut), and Inuit hunting all
increase the species’ vulnerability. There is genetic
evidence (one of the lowest measures of genetic
diversity of all marine mammals) that the narwhal
went through an earlier bottleneck, but survived.
Climate change, as it occurs, will alter ocean
temperatures, currents, ice formation, and sea
level. These changes will affect a broad variety of
sea mammals, not just narwhal. Cetaceans will be
among the most vulnerable and likely to be
negatively affected. Cetaceans would be affected
by changes in their prey both in terms of
productivity and shifts in distribution of prey
species.
Five other related issues:
(1) The rate of climate change is outside the
evolutionary experience of existing cetacean
species.
(2) Many whale species have complicated life
cycles and appear to be dependent on finding
certain resources in certain places at certain
times.
(3) Movement of water bodies and changes in
temperature could affect the ability of whales to
navigate across the oceans.
(4) Many whale populations are already at
extremely low levels.
(5) Species and populations are concurrently
being negatively affected by other factors.
Here’s a table of marine mammals and their
conservation status (from Simmonds and Isaac 2007):
What will the effects on marine mammals be?
Colder water species will shift towards the poles and,
ultimately, this will probably result in a reduced
global range for these species. Some of this is
response to changes in prey distribution. Example:
Cetacean relative abundance in north-west Scotland
suggested a range expansion of common dolphins
Delphinus delphis (a warmer water species) and a
decrease in range of white-beaked dolphins
Lagenorhynchus albirostris.
It is not only the large mammal species that will be
affected. Melting has increased the input of fresh
water into many areas of the North Atlantic (Greene et
al. 2008). That change in salinity in coastal shelf
regions is affecting abundances and seasonal cycles of
phytoplankton, zooplankton, and higher trophic-level
consumer populations.
There are also a renewed, ongoing series of
biogeographic range expansions by boreal plankton,
including renewal of the trans-Arctic exchanges of
Pacific species with the Atlantic, e.g. the North Pacific
diatom species Neodenticula seminae.
Application of Predicted Climate to Specific
Examples
1)Mammals on Mountaintops (and associated
communities)
Loss of diversity of boreal small mammals from
montane forests of the isolated mountain ranges in
the Great Basin of the western is predicted in the
U.S. (Brown 1995, 1998). A model of the loss was
developed based on a doubling of CO2 and a 3o rise
in average temperature. Boreal woodland will
move up the mountain by 500m. That significantly
decreases the habitat area available to the small
mammals.
Using species-area relationships for these species that
Brown had determined earlier, he was able to predict
species losses on each of 19 mountain ranges.
Brown went on to predict exactly which small
mammals would disappear from which mountains…
Common names for species in the previous table
Eutamias – chipmunk
Neotoma – packrat
Spermophilus – ground squirrel
Microtus – vole
Silvilagus – cottontail rabbit
Marmota – marmot
Sorex – shrew
Mustella – weasel (this one is the ermine)
Ochotona – pika
Zapus – jumping mouse
Lepus - hare
2) Range shifts in temperate, deciduous trees of
the Great Lakes region
Zapinski and Davis (1989, described in Brown 1998)
determined that a number of Great Lakes area tree
species had northern limits corresponding to the -15ºC
January isotherm. They used the last post-glacial
period to estimate the rate at which tree species could
migrate, using an artificially high estimate of 100
km/century. Distributions on the next slide show the
current distribution on the left, predicted distribution
for the end of this century on the right. The gray area
indicates the long-term potential distribution given
sufficient time for dispersal into new areas.
3) Range shifts in European butterflies and
Monarch Butterflies
Parmesan et al. studied ranges of non-migratory
butterflies over the last century in Europe (Parmesan,
et al. 1999). Each species had the northern limit of its
range in northern Europe, and the southern limit in
southern Europe or northern Africa. Data forced them
to study northern and southern limits separately.
Northern boundaries moved northward in 65% of 52
species, remained stable in 34%, and moved
southward in one species (2%). This is a highly
significant result (P << 0.001).
Southern boundaries retracted northwards in 22% of
40 species, remained stable for most (72%) and moved
southward for two species (5%). This is not a
significant northward movement.
Changes in northern and southern boundaries could be
evaluated together for 35 species. Of these, 63%
shifted northwards, 29% were stable at both
boundaries, 6% shifted southwards, and 3% extended
range both northward and southward. This is a highly
significant result.
The distance these species moved northward ranged
from 35-240 km. Annual mean temperatures have
warmed by about 0.8° C during the 20th century.
Does this mean that species can adapt to climate
change? Yes and no. When climate changes slowly
enough, many species can keep up. However, the
projected change in temperature during the 21st
century is far larger, estimated as 2.1 – 4.6C.
4) Thermal stress in Intertidal Marine Species
Helmuth et al. (2002) suggests intertidal species like
mussels that live in intertidal areas must be able to
withstand aerial exposure during low tides,
potentially placing these organisms in thermal stress.
The intertidal mussel Mytilus californianus is found
along a latitudinal gradient from California to
Washington. Study showed that midday exposure of
mussels to high temperature will be greater at higher
latitudes than at lower ones, in part because variation
in tide height will be more pronounced at the higher
latitudes.
Moreover, areas that sustain higher water
temperatures may also experience higher feeding
rates by predators (sea stars) whose metabolic
activity is positively linked to water temperature.
5) Pending Global extinctions associated with
climate change
What is expected to happen to biodiversity between
now and 2050 if the world warms according to
reasonable projections?
If we assume that climate warming will reduce
suitable habitat areas, then Thomas et al. (2004)
determined average extinction risk probabilities for 3
warming scenarios:
0.8 to 1.7° increase: 18% species loss
1.8 to 2.0° increase: 24% species loss
>2.0° increase: 35% species loss
References and Readings:
Baxter, M.S. and A.Walton. 1970. A theoretical approach to the Suess effect.
Proc.Roy.Soc. London A 318:213-230.
Brown, J.H. 1995. Macroecology. Univ. Chicago Press, Chicago, Ill.
Brown, J.H. and M.V. Lomolino. 1998. Biogeography 2nd ed. Sinauer, Sunderland,
MA. P.567-9, 601-12.
Greene, C.H., A.J. Pershing, T.M. Cronin and N. Ceci. 2008. Arctic climate change
and its impacts on the ecology of the North Atlantic. Ecology 89:S24-38.
Helmuth, B., C. Harley, P. Halpin, M. O’Donnell, G. Hofmann, and C. Blanchette.
2002. Climate change and latitudinal patterns of intertidal thermal stress. Science 298:
1015-1017.
Hughes, L. 2000. Biological consequences of global warming: is the signal already
apparent? TREE 15:56-61.
Laidre, K.L. and M.P. Heide-Jorgenson. 2005. Arctic sea ice trends and narwhal
vulnerabiulity. Biol.Conserv. 121:509-517.
Lorius, C., J. Jouzel, C. Ritz, L. Merlivat, N.I. Barkov, Y.S. Korotkevich and V.M.
Kotlyakov. 1985. A 150,000-year climatic record from Antarctic ice. Nature 316:59196.
Oberhauser, K. and T. Peterson. 2003. Modeling current and future potential
wintering distributions of eastern North American monarch butterflies. Proc. Nat.
Acad. Sci. (USA): 100: 14063-14068.
Parmesan, C. and G. Yohe. 2003. A globally coherent fingerprint of climate change
impacts across natural systems. Nature 421:37-42.
Parmesan, C. et al. 1999. Poleward shifts in geographical ranges of butterfly species
associated with regional warming. Nature 399:579-583.
Root, T.L. et al. 2003. Fingerprints of global warming on wild animals and plants.
Nature 421:57-60.
Stainforth, D.A. et al. 2005. Uncertainty in predictions of climate response to rising
levels of greenhouse gases. Nature 433:403-406.
Thomas, C.D. et al. 2004. Extinction risk from climate change. Nature 427: 145-148.
Zabinski, C. and M.B. Davis. 1989. Hard times ahead for Great Lakes forests: A
climate threshold model predicts responses to CO2-induced climate change. In J.B.
Smith and D. Tirpak, eds. The Potential Effects of Global Climate Change on the
United States. Appendix D, U.S. E.P.A. Washington, D.C.