Climate Change: The science

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CLIMATE CHANGE: THE SCIENCE

UNDP-GEF CBA WorkshopJune 30 2009

Michael A. TaylorClimate Studies Group, Mona

Department of PhysicsUniversity of the West Indies, Mona

QUIZ #1UNDP_GEF UNDP_GEF CBACBA

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Why Change?How Change?More Change?We Change?

Weather, climate, climate variability, climate change – all these terms are sometimes confusing.

A. Yes

B. No

C. Not really, but remind me anyway about them.

WEATHER AND CLIMATEUNDP_GEF UNDP_GEF CBACBA

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Weather

Day to day (short term) changes in meteorological parameters – rainfall, temperatures, pressure, etc.

Often perceived in terms of extreme events: heat waves, downpours, cold spells .

Climate

Commonly defined as the “average weather”. Mean and variability of weather over a periods of time ranging from months to thousand/millions of years.

That concerning the status of the entire Earth system, (atmosphere, land, oceans, snow, ice and living things) which serve as the global background condition for determining weather patterns (IPCC 2007)

VARIABILITY AND CHANGE

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Regular

Irregular

Long TermTrendy

UNDP_GEF UNDP_GEF CBACBA

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VARIABILITY AND CHANGE

In any climate timeseries multiple timescales of variation exist.

Climate Variability - Regular, Irregular, Long Term

Timescales that are ‘short term’ – seasonal, annual, interannual (every few years), even decadal. – ENSO, AMO, PDV

Good harbinger for climate change impacts.

Climate Change – Trendy

Distinct changes in measures of climate lasting for a long period of time e.g. major changes in temperature, rainfall, snow, or wind patterns lasting for decades or longer.

Variability and Change and Weather Extremes interrelated.

Will examine climate change.



Possible contributors to Climate Change include:

A. Changes in the earth’s orbit

B. Volcanic eruptions

C. Burning of fossil fuels

D. All of the above

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CLIMATE CAN CHANGE DUE TO...

Natural Variations

Volcanic Eruptions Human Activity

•Changes in the earth’s orbit

•Changes in solar intensity

•Preindustrialized era e.g. Ice Ag

•Alter aerosols in the atmosphere (block sunlight) … not long term effect.

•Alter carbon dioxide concentrations (CO2)

•Alter aerosols in the atmosphere (block sunlight) … not long term effect.

•Alter carbon dioxide concentrations (CO2)

•Changing land cover (reflective properties of earth).

•Altering aerosol concentrations.

•Post Industrial Revolution (~1750). Burning of fossil fuels and biomass has altered the composition of the atmosphere primarily through the addition of greenhouse gases.


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GREENHOUSE GASES?

Purpose: Glass house to keep plants warm during winter.

How works?

•Sun’s rays hit the glass

•Some rays immediately reflected

•Some pass through glass and reach plants. Inside gets hot.

•Heat cannot escape due to glass.

•Glass very important!!!


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GREENHOUSE GASES?

Atmosphere around earth is like the glass!!!

How works?

• Solar radiation hits atmosphere

•30% reflected. 70% reaches the earth

•Earth warms and gives off heat.

•Certain gases in atmosphere prevent most of heat escaping. E.g. CO2, methane, H2O, ozone, nitrous oxide

Called greenhouse gases!!!


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GREENHOUSE GASES?

Greenhouse effect is not a bad thing = warm (habitable) earth!!

Problem

Since the Industrial Revolution humans have added a significant amount of greenhouse gases in the atmosphere by burning fossil fuels, cutting down forests and other activities.


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GREENHOUSE GASES?

CO2

A 36% Increase from pre-industrial times. Almost all of the increase is due to human activities (IPCC, 2007) .

CH4

Now 148% above pre-industrial levels. (IPCC, 2007) .


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GREENHOUSE GASES?

Radiative Forcing

How the energy balance of the earth-atmosphere system is altered by factors that affect climate.


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GREENHOUSE GASES?UNDP_GEF UNDP_GEF CBACBA

IPCC (2007)

It is extremely unlikely (<5%) that the global pattern ofwarming during the past half century can be explainedwithout external forcing, and very unlikely that it is dueto known natural external causes alone.


Which of the following changes has been observed in the last century:

A. Warmer temperatures

B. More rain

C. Less rain

D. All of the above

E. None of the above

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GLOBAL WARMING

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Global warming is an average increase in temperatures near the Earth’s surface and in the lowest layer of the atmosphere.


GLOBAL WARMING

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IPCC:

Global warming is unequivocal!

There is a greater than 90 percent chance that most of the warming we have experienced since the 1950s is due to the increase in greenhouse gas emissions from human activities.


TEMPERATURES

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• Global mean surface temperatures continue to rise.

• Earth is 0.75 degrees warmer than in 1860.

• 11 of the last 12 years rank among the 12 warmest years on record since 1850.

• 7 of 8 warmest years on record have occurred since 2001. • In last 30 years, the rate of warming across the globe has been approximately 3 x greater than the rate over the last 100 years.


TEMPERATURES

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• The warming trend is seen in both daily maximum (day time) and minimum (night time) temperatures.

•Minimum temperatures increasing at a faster rate than maximum temperatures.

•Land areas have tended to warm faster than ocean areas.

•‘Winter’ months have warmed faster than summer months.


SEA LEVEL RISE

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Primary factors driving current sea level rise include:

•the expansion of ocean water caused by warmer ocean temperatures

•melting of mountain glaciers and small ice caps

•(to a lesser extent) melting of the Greenland Ice Sheet and the Antarctic Ice Sheet


SEA LEVEL RISE

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IPCC (2007)

•Most of the Pacific and Atlantic basins are experiencing average to above-average sea level rise.

•the rate of observed sea level rise increased from the mid 19th to the mid 20th century. During the 20th century, sea level rose at an average rate of 4.8 to 8.8 inches per century (1.2-2.2 mm/year)

• Satellite measurements estimate that sea level has been rising at a rate of 9 to 15 inches per century (2.4-3.8 mm/yr) since 1993.


RAINFALL

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Rainfall patterns changing. IPCC (2007)

•Significant changes in amount, intensity, frequency and type of precipitation.

•Trends vary widely by region and over time.

•Precipitation strongly modulated by variability e.g. ENSO.

•Globally there has been no statistically significant overall trend in precipitation over the past century.


RAINFALL

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Rainfall patterns changing. IPCC (2007) •Precipitation has generally increased over land north of 30°N from 1900-2005, but has mostly declined over the tropics since the 1970s.

•Wetter in eastern North and South America, northern Europe and northern and central Asia, but drier in the Sahel, southern Africa, the Mediterranean and southern Asia.

•More precipitation now falls as rain rather than snow in northern regions.


RAINFALL

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IPCC (2007)

•There has been an increase in the number of heavy precipitation events over many areas during the past century, as well as an increase since the 1970s in the prevalence of droughts — especially in the tropics and subtropics.

•The long-term record emphasizes that patterns of precipitation vary from year to year, and even prolonged multi-year droughts are usually punctuated by a year of heavy rains; for instance as El Niño influences are felt.

Proportion of heavy rainfall is increasing over many land areas


EXTREME EVENTS

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IPCC (2007)

•Since 1950, the number of heat waves has increased and widespread increases have occurred in the numbers of warm nights.

•The extent of regions affected by droughts has increased as precipitation over land has marginally decreased .

• Generally, numbers of heavy daily precipitation events that lead to flooding have increased, but not everywhere.

•In the extratropics, variations in tracks and intensity of storms reflect variations in major features of the atmospheric circulation, such as the North Atlantic Oscillation.

•Tropical storm and hurricane frequencies vary considerably from year to year, but evidence suggests substantial increases in intensity and duration since the 1970s.


CARIBBEAN EXAMPLE

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Study done at UWI and NCDC

•Tmax, Tmin, rainfall station data. 1950-2000

•Looking if climate extremes have changed in Caribbean in recent history.Peterson, T. C., M. A. Taylor, et al., 2002:

Recent changes in climate extremes in the Caribbean region, J. Geophys. Res., 107(D21)


CARIBBEAN EXAMPLE

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Why Change?How Change?More Change?We Change? •Frequency of Hot days and

hot nights increasing (nights > days)

•Frequency of cool days and nights decreasing

• Trendlines significant at 1% level

•Frequency of cool days and nights decreasing

•True for rest of world.



A climate model is:

A. A tool to help us determine future climates

B. A person hired by IBM to show their product

C. A person hired by Mac to show their product

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CLIMATE MODELS

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COMPUTER MODELS

•A set of physics based equations to describe processes of atmosphere.

•Prescribed boundary and initial conditions.

•Start with real time and simulate into future (most times to end of century).

•Can produce projections of rainfall, temperature, wind, pressure, cloud cover, humidity and a suite of other variables for a day, month, or a year in the future.


CLIMATE MODELS

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General Circulation Models (GCMs)

•Horizontal resolution: 250-600 km•10-20 vertical layers in the atmosphere•As many as 30 ocean layers

Regional Climate Models (RCMs)

•Use outputs from GCM as boundary conditions•Horizontal resolution: 25-50 km •Small islands can be resolved.

EMISSION SCENARIOS

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•To generate projections with

the climate models we have to

make up stories about how the

world will evolve in the future.

SCENARIOS = STORYLINES


EMISSION SCENARIOS

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Most common: IPCC Special Report of Emissions Scenarios (SRES)

•Storylines depend on what population growth, energy use, economic development and technology could look like in the future.

•A and B families are created to represent different storylines with similar attributes.

•Storylines give us estimate of

future greenhouse gas

concentrations.


EMISSION SCENARIOS

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A2 (High Emissions)•Continuously increasing population•Regionally oriented economic development•Technological change more fragmented

A1B (Intermediate Emissions)•Global population peaks in mid-century and declines thereafter•Rapid economic growth•Balance across fossil and non-fossil energy sources

B1 (Low Emissions)•Population peaks mid-century and declines thereafter•Rapid change towards a service and information economy•Introduction of clean and efficient technologies

None involves the stabilization of concentrations of greenhouse gases!!


PROJECTIONS

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Models + Scenarios = Future Climate

Projection: A potential future evolution of a quantity or set of quantities. Not the same as a Prediction since projections involve some assumptions about the future –and are therefore open to a great deal of uncertainty.


TEMPERATURES

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CommitmentNo increase in greenhouse gas concentrations from 2000

Emission Scenarios


TEMPERATURES

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End of century

Commitment = 0.6 degrees

Best-Worst: 1.5 – 5 degrees

Near-term warming projections are little affected by different scenario assumptions. By 2030 change lies in narrow range of 0.64°C to 0.69°C .


TEMPERATURES

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Global mean surface temperatures

End of century (A18 medium emissions scenario)

Geographic patterns show greatest temperature increases at high northern latitudes and over land, with less warming over the southern oceans and North Atlantic.


RAINFALL

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Regional changes (+/-) of up to 20% in average rainfall

Generally, robust large-scale patterns: precipitation generally increases in the tropical precipitation maxima, decreases in the subtropics and increases at high latitudes as a consequence of a generalintensification of the global hydrological cycle.

But…Model projections for extremes of precipitation show larger ranges in amplitude and geographical locations than for temperature.

The response of some major modes of climate variability such as ENSO differs from model to model.


SEA LEVEL RISE

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•Sea level will continue to rise in the 21st century because of thermal expansion and loss of land ice.

•Sea level rise was not geographically uniform in the past and will not be in the future.

•Projected warming due to emission of greenhouse gases during the 21st century will continue to contribute to sea level rise for many centuries.

•Sea level rise due to thermal expansion and loss of mass from ice sheets would continue for centuries even if radiative forcing were to be stabilised.


EXTREMES

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•Type, frequency and intensity of extreme events are expected to change as Earth’s climate changes.

•Changes could occur even with relatively small mean climate changes.

•Changes in some types of extreme events have already been observed .

Other…Heat waves become more frequent and longer lasting in a future warmer climate.

Increased summer dryness and winter wetness in most parts of the northern middle and high latitudes

Precipitation tends concentrated into more intense events, with longer periods of dry in between .

Evidence from modelling studies that future tropical cyclones could become more severe, with greater wind speeds and more intense precipitation.


CARIBBEAN EXAMPLE

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End of century temperature change (PRECIS RCM)

•Irrespective of scenario Caribbean expected to warm

•Warming between 1and 5 degrees.

•Warming greater under A2 scenario

•Warming consistent with projections for other parts of the globe


CARIBBEAN EXAMPLE

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End of century % rainfall change (PRECIS RCM)

•For both scenarios Caribbean is in general drier.

•Up to 30% drier.

•Drying more severe under A2 scenario

•Far north Caribbean however could be wetter



In light of all this, should we be concerned?

A. Yes

B. Absolutely yes

C. Yeah Man!

D. This is a rhetorical question, right?

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CONFIDENCE

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In light of everything, should we change how we operate?

Perhaps depends on how confident we are about the projected changes.

Confidence in the models comes from the following:

1.Model fundamentals are based on established physical laws, such as conservation of mass, energy and momentum, along with a wealth of observations.

2.Models ably simulate important aspects of the current climate. Reasonable skill in representing important features of the general circulation across shorter time scales, and aspects of seasonal and interannual variability.

3.Models ably reproduce features of past climates and climate changes.

4.Over several decades models have consistently provided a robust and unambiguous picture of significant climate warming in response to increasing greenhouse gases.


CONFIDENCE

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So…

Though models still show significant errors (mainly due to important small-scale processes not being represented explicitly in models) there is considerable confidence that they are able to provide credible quantitative estimates of future climate change, particularly at larger scales.


IMPACT WILL BE WIDELY FELT...

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CARIBBEAN EXAMPLE

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Dengue

CARIBBEAN EXAMPLE

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Hot Wet Dengue

Time series graph of rainfall, dengue cases & average temperature(4-Week periods in Trinidad & Tobago)

0

200

400

600

800

1000

1200

1400

0 20 40 60 80 100

Year

Rain

fall

(m

m)

Re

porte

d d

engu

e

25

26

27

28

29

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32

Aver

age

tem

perta

ure

(C)

Rainfall Dengue Cases Average Temperature

1996 1997 1998 1999 2000 2001 2002 2003

CARIBBEAN EXAMPLE

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Linkage to El NiñoDue to rainfall and temperature

changes

CARIBBEAN EXAMPLE

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Estimated that a future 2 degree rise in temperature will cause an increase in incidence of dengue in

the Caribbean region.

SUMMARY

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Why the Change?Greenhouse gas forcing has very likely caused most of

the observed global warming over the last 50 years.

How has the Change been manifested to date?Global mean surface temperatures continue to rise.

Eleven of the last 12 years rank among the 12 warmest years on record since 1850.

Other changes in precipitation patterns, sea levels and extreme events have also been observed.

Will there be More Change in the future?Even if concentrations of radiative forcing agents were to be stabilised, further committed warming and related climate changes would be expected to occur.


SUMMARY

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Should We Change our mode of operating?

We live in a climate sensitive world. This makes us vulnerable to climate variability and change. It would be foolish to continue to operate as normal. We must begin to consider appropriate actions to enable quality lifestyles in the future.



Is this the end of this talk?

A. Yes

B. Yes

C. Yes

D. No, let’s start it all again

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END

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Thank You


Climate Change: The science

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