Climate Change. In the last 90 years the Earth’s mean temp rose 0.6 o C, a rate not seen in 10K yrs The scientific facts are clear and the vast majority.

Climate Change

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Climate Change

• In the last 90 years the Earth’s mean temp rose 0.6oC, a rate not seen in 10K yrs

• The scientific facts are clear and the vast majority of climatic scientists have determined that the major cause is anthropogenically produced greenhouses

(but don’t call global warming)

Climate Change

• However, the most influential discussions are in the policy and public arenas

• What does anthropogenic climate change signify for the future?

• Is climate change reversible? • How quickly will weather patterns change?• What can be done to mitigate the

detrimental effect of altered climates?• How will new climatic patterns influence

species’ distributions and biodiversity?

The Nature of Climate Change

• Generally, climate shifts have been caused by changes in retention and distribution of solar energy across the planet

• Solar radiation passes through the atmosphere as short wavelength ultraviolet (UV) wavs

Climate Change

• Fig 10.1

The Nature of Climate Change

• The most important gases in the energy balance are CO2, CH4, and H2O as these cannot be penetrated by radiation in the infrared spectrum (long-wave)

• These ‘greenhouse’ gases keep the earth approximately 60oC warmer than would be expected without them

Climate Change through Time

• Since the industrial revolution, burning fossil fuels has increased greenhouse gases by about 30%

• However, we know there is always variation in systems

• Historically, we have been cooling since the Tertiary period (50-60MYA)..10oC


• Average global temperature over last 65MY. Gray indicate hotter than current, black cooler. Note from 2MYA to 12KYA strong cycles


• Looking at a finer time scale we can see fluctuations throughout the Pleistocene (1.8MYA to 12KYA)

• The Milankovitch cycles match the Earth’s orbit and tilt relative to the sun and drives the temperature cycle through a series of positive and negative feedbacks


• Small bubbles trapped in ice of Antarctica yield info on atmospheric composition

• Furthermore, ration of 18O2 to 16O2 can accurately record temperature

• This approach has yielded a relatively accurate temperature history going back 740KYA


• Relationship between temperature and CO2 over past 160K yrs.

• Note the current elevated CO2 levels


• It is important to remember the impact of relatively small changes

• E.g. peak glacial periods were only about 5oC cooler than current temperatures

• Our current warming trend will push it to one warmer than was ever experienced during the Pleistocene period

Human Enhancement of Greenhouse Effect

• The insulating properties of CO2 were discovered in the mid-1800’s

• CO2 has rose 36% since 1910, which is well outside historical ranges

Current and Future Climate and Change

• Scientists have developed a series of global climate models (GCMs) based upon the processes by which atmospheric greenhouse gases affect global climate

• The models vary based upon different rates of gas emission (what affects rate?)

• All models suggest warming should be greatest at the poles, least in the tropics


• E.g. in some parts of AL, Canada and Siberia mean annual has risen 2-4oC since 1900

• Another pattern is the lack of nights below freezing in the mid-latitudes (fig 10.6)

• Another pattern is the change is precipitation (especially in intensity), but again, not consistent everywhere


• Black indicates warming and gray indicates cooling

• Size indicates magnitude of change


• Black is wetter and gray is drier

• Size indicates magnitude of change


• Ironically, the GCMs all suggest continued increase in precipitation, but with warmer climate, evapotranspiration is increased

• Furthermore, the variance in precipitation events gets larger

• What is the impact of larger variances but not means?

Oceans: Sea Level and Circulation

• Is beach front property consistent?• 20KYA, sea levels were as much as

120m lower than current levels• Annual changes are relatively small

(e.g. 0.1-0.2mm) over past 3K yrs• However, past 200 yrs there has been

rapid rising of ocean levels due to two factors: precip, ice caps (.2-.4mm) and thermal expansion (1mm annually)


• Sea levels rise over 3K yrs in 3 Euro cities


• Major ocean circulation systems are already showing signs of being affected by the rise in atmospheric temperatures

• El Niño (and La Niña) events have increased in frequently and intensity (warming of mid-Pacific, pushing into cold waters)

• Some models predict by 2050 “normal” years will resemble current El Niño yrs


• Warm H2O surges in cold water areas


• Snow, Ice, and Hydrological changes• Widespread retreat of glaciers in N &

S Am, NZ, Af, Europe and Asia• (e.g. GNP, 70% glaciers lost…gone

2020)• (e.g. Mt Kilimanjaro 60%)• Approximately 30% of projected sea

change will come from glacial melt


• Another problem is flood events rather than water soaking into the soil

• In many areas, H2O comes in the form of snowfall with gradual melting feeding streams/rivers throughout summer

• Spring melts are occurring earlier


• Glacial retreat (1973 and 2000)

Predicted Biological Impacts

• So many biological processes are tied to climatic events, the idea that these will change may have profound impacts

• One approach to better understand the potential impact is to identify species’ distributions and their ‘climate envelope” from manipulative studies

• For an in-depth look, Case Study 10.1


• A simplistic view of biotic responses is that species may simply alter their distribution quickly (e.g. birds) or gradually (e.g. seed dispersal)

• Paleoecologists have found many communities found together no longer co-occur

• Why?

Predicted Biological Impactsextreme weather

• Many systems are strongly influenced by climate and weather extremes

• E.g. frost boundaries and plants• E.g. precipitation limits animals & plants

– Drought in NM in 1950’s, pine and p-j, 2km– 9-banded armadillo, 39cm and <24 freezes

• Single events can have long-term affects– Drought and Darwin’s finches– Warm water events, bleach coral reefs


• Prolonged climate swings can impact– Map turtles; 28oC<M and >30oC F

• Many insect populations boom/bust with climatic events

• Host-parasite and infectious diseases are strongly influenced by climate

• Even if extremes don’t increase, their frequency may increase


• Increases in mean temperature, leading to more record temperatures

Observed Biological Impacts

• An increase in both mean and variance temperatures


• Detection and Attribution• It is extremely important to determine

the relative impact of climate change• Won’t review the evidence on CC• Studies examining the impact of CC

on wildlife are by nature, correlative rather than experimental (FACE-free air CO2 Exchange)

• Attribution now a priority for many


• Evolutionary & Morphological Changes• Because of the rapid nature of CC, little

discussion of evolutionary adaptations– Drosophila subobscura from N Euro had

longer wings than S, 20 yrs adjusted to the climate envelop (more similar to S Euro)

– E.g. Desert rodents have gotten 16% smaller body size… why?


• Phenological Shifts (e.g. amount of daylight, seasonal weather) in organisms (e.g. arrival of migratory birds)

• Many biological events are temp driven (e.g. leaf emergence, turtle hatching)– E.g. in AZ, MEJA hatch 10 days (’71 to ’98)– Many other examples (ice out, spring bloom)– European amphibian breeding advanced

• There can be desynchronization…BTBW

Abundance Change and Community Reassembly

• Climate can have a direct impact on populations and communities– E.g. BTBW and El Niño (S) and La Niña

(W)

• Community structure has been changed– In CA waters, warming waters have

favored a different plant community


• Mean annual ocean temperatures at Scripps


• Southern species have increased in abundance while Northern species have decreased

in S CA


• In terrestrial communities, there has been woody incursion into grasslands

• In experimental communities, increases in temp, H2O, and CO2, all result in increases in woody species

Range Shifts

• Species ranges are dynamic, changing both spatially and temporally

Range Shifts

• There are many examples of range shifts in apparent direct response to CC

• In N Am and Europe, 2/3 of butterflies (n=58) studied have shifted N by 100km per decade

• Montane studies have shown plants and animals are being found at higher elevations

Range Shifts

• Patterns of population extinction of Edith’s checkerspot butterfly Eupydryas editha from 1860 to 1996

• Note significantly higher extinction in N

• Black present, gray extinct

Range Shifts

• Overwintering range of the sachem skipper butterfly, which is limited by repeated to exposures to -4oC

Synthesis of Impacts

• Is there a bias in our conclusions about the impact of CC? “positive publishing”

• A meta-study (1700 sp), about ½ the sp were stable

• However, 50% exhibited significant responses to regional warming (e.g. phenology or distributional shifts)

• Table 10.1

Conservation Implications of CC

Extinctions • There has been a spike in extinctions

in recent centuries• There have only been 2 extinctions

directly attributable to CC (2 trop frog)

• Abundance of zooplankton off CA has declined by 80%...and sp relying on this food base are in trouble


Extinctions • The ability to track changes is

important for species’ survival• Unfortunately, many endangered sp

tend to have such traits (e.g. limited dispersal, small ranges, strong local adaptation)

• Constructing a ‘climate envelope’ of threshold values (of precip and temp) can help predict impacts of species


Extinctions • Range shift model of a S Af plant


Extinctions • A synthesis study of extinction risk

estimates suggests a rough estimate of extinctions by 2050

• With perfect dispersal and minimal reduction in climate envelope, ranges from about 9-13% of sp would go extinct (1.2oC) to 21-32% (2oC)

• Note: these estimates are strictly climate-based. Other problems?

Responses to CC by Managers

• Most managers and conservation planners focus on local-scale projects

• Climate shifts cause problems for locals because they don’t account for climate

• Consequently, they need climate models that are not only accurate, but at a spatial scale relevant to locals

Responses to CC by Managers

• There are adaptive approaches managers could use– Susceptibility analysis of impact of CC– Design/adjust reserve to allow movement– Promote corridors – Create dynamic habitat conservation plans– Alleviate nonclimate stressors– Generalization of climate prediction models

CC and Conservation Policy

• The widescale potential impact of CC makes is potentially more important than any other conservation issue

• Marketing 101: Global CC is a local issue

• Policy issues are difficult to achieve due to the potential costs and ‘fairness’

• There are many, many issues here…

Climate Change

Climate Change. In the last 90 years the Earth’s mean temp rose 0.6 o C, a rate not seen in 10K yrs The scientific facts are clear and the vast majority.

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