Climate change: Climate change: the sciencethe science

OutlineOutline

Greenhouse effectGreenhouse effect Methods used to gather dataMethods used to gather data The data-what does it tell us?The data-what does it tell us?

Long-term temperature recordsLong-term temperature records Historical climate changesHistorical climate changes Greenhouse gas recordsGreenhouse gas records Current emissionsCurrent emissions

Weather vs ClimateWeather vs Climate

Weather: what you should wear outside on a particular day

Climate: the kinds of clothes you should buy

Translation: weather gives us information about short periods like hours or days while climate gives us a long-term picture, usually over decades or centuries

What are Greenhouse What are Greenhouse Gases?Gases?

The normal atmosphere: 78% The normal atmosphere: 78% nitrogen, 21% oxygen, and trace nitrogen, 21% oxygen, and trace amounts of other gases (1%)amounts of other gases (1%)

Gases that absorb heat in the Gases that absorb heat in the atmosphere: water vapor, carbon atmosphere: water vapor, carbon dioxide, methane, nitrous oxidedioxide, methane, nitrous oxide

5 layers of the 5 layers of the atmosphereatmosphere

We focus on the troposphere and stratosphere because that is where most natural processes occur (gases are often trapped in the stratosphere)

Greenhouse effect: good or Greenhouse effect: good or bad?bad?

Keeps average temperature around 60 FKeeps average temperature around 60 F Without it, avg. temps would be about 0 Without it, avg. temps would be about 0

FF Venus: atmosphere of CO2 (96%) and Venus: atmosphere of CO2 (96%) and

nitrogen- the avg. temperature is 885 F nitrogen- the avg. temperature is 885 F (very high atmospheric pressure; 90 (very high atmospheric pressure; 90 times that on earth)times that on earth)

=Goldilocks principle

How do scientists How do scientists “know”“know” the climate the climate

has changed?has changed?

Ice coresIce cores

Tree RingsTree Rings

Sediment LayersSediment Layers

Coring Staten Island salt marsh marsh

Core section

Tundra pollen typesTundra pollen types

CyperaceaeCyperaceae

Gramineae

PhenologyPhenology

A study of the A study of the times of times of recurring recurring natural natural phenomena: phenomena: migrations, migrations, tree/flower tree/flower budding, ice budding, ice cover on cover on lakes, mating lakes, mating of organismsof organisms

Climate Change & LilacsClimate Change & Lilacs

www.gardencorner.net

72 locations in the Northeast studied from 1965 to 2001

Monitored for first leaf and first flower dates

Results: plants showing signs of spring between 2 and 8 days earlier

The data…should we be The data…should we be worried?worried?

Increasing TemperaturesIncreasing Temperatures

Carbon dioxide and temperature levels are correlated

Long-term Climate on Long-term Climate on EarthEarth

Earth is currently in an ‘icehouse’ state that Earth is currently in an ‘icehouse’ state that began 34 million years ago and includes began 34 million years ago and includes several ice agesseveral ice ages

750 to 580 million years ago: in three separate 750 to 580 million years ago: in three separate instances, the earth froze over from the poles instances, the earth froze over from the poles to the equator and then melted back outto the equator and then melted back out

440 million years ago: ice age lasting only 1 440 million years ago: ice age lasting only 1 million years and may have contributed to the million years and may have contributed to the extinction of 85% of all plant and animal extinction of 85% of all plant and animal species species

330 to 270 million years ago: series of cold 330 to 270 million years ago: series of cold intervals during which ice covered the intervals during which ice covered the southern hemispheresouthern hemisphere

Feedback Feedback LoopsLoops

IPCC

Major Greenhouse GasesMajor Greenhouse Gases

Water vapor (majority of GG)Water vapor (majority of GG)

Carbon dioxide (COCarbon dioxide (CO22): longest ): longest residence timeresidence time

Methane (CHMethane (CH44))

Nitrous oxide (NNitrous oxide (N22O): strongest O): strongest warming potentialwarming potential

Why care so Why care so much about much about

carbon dioxide?carbon dioxide?

Emphasis has been placed on COEmphasis has been placed on CO22 emissions because emissions because

It will contribute more than half of the increase in It will contribute more than half of the increase in radiative forcing during the next 100 years radiative forcing during the next 100 years

It’s long residence time in the atmosphere-ocean system It’s long residence time in the atmosphere-ocean system We know source and can stop itWe know source and can stop ithttp://www.npr.org/templates/story/story.php?storyId=15662891

Image source: U

.S. F

ish and Wildlife

Service

2009: carbon dioxide is at 387 ppm

Changes since pre-Changes since pre-industrial timesindustrial times

Carbon dioxide up Carbon dioxide up 35%35%

Methane up 155%Methane up 155% Nitrous oxide up Nitrous oxide up

18%18%

CO2 higher now CO2 higher now than anytime in the than anytime in the past 600,000 years past 600,000 years

Past Variations in Past Variations in

Atmospheric COAtmospheric CO22

High concentrations before evolution High concentrations before evolution of land plantsof land plants

Between 100 - 400 ppm over the past Between 100 - 400 ppm over the past 20,000,000 years (Pearson and 20,000,000 years (Pearson and Palmer, 2000).Palmer, 2000).

For the past 2000 years, For the past 2000 years, concentrations of COconcentrations of CO22 remained remained between 270 and 290 ppm.between 270 and 290 ppm.

……Until the Industrial Until the Industrial RevolutionRevolution

Most recent projections from the IPCC Most recent projections from the IPCC (IPCC, 2001) are for levels reaching (IPCC, 2001) are for levels reaching 500 ppm in 2050 500 ppm in 2050 > 700 ppm by 2100.> 700 ppm by 2100.

due to massive human perturbation of due to massive human perturbation of the Carbon Cycle.the Carbon Cycle.

Global Trend: Increasing Global Trend: Increasing Greenhouse GasesGreenhouse Gases

Forster et al, 2007

Global budgetGlobal budget: An account—like : An account—like a checkbook—of the additions and a checkbook—of the additions and withdrawals of an element from a withdrawals of an element from a reservoir—like the atmosphere—reservoir—like the atmosphere—over a given period of time over a given period of time (Schlesinger, 1997).(Schlesinger, 1997).

© Dr. Anthony R. Picciolo, NOAA

Biogeochemists assess the emissions of CO2 to the earth’s atmosphere and forecast global budgets

Sources & SinksSources & Sinks What’s a source? What’s a source?

Anything that adds CO2 to the atmosphere Anything that adds CO2 to the atmosphere (natural or man-made)(natural or man-made)

What’s a sink? What’s a sink? Anything that removes CO2. Anything that removes CO2.

Who cares? Who cares? Up till now, the annual growth of Up till now, the annual growth of

atmospheric CO2 has been smaller than atmospheric CO2 has been smaller than emissions, because of the presence of emissions, because of the presence of natural sinks. New research believes the natural sinks. New research believes the ocean is done being a sink. ocean is done being a sink.

Graphic: Jerry Jenkins, WCS

Graphic: Jerry Jenkins, WCS

Human Perturbation of the Human Perturbation of the Global Carbon CycleGlobal Carbon Cycle

Oil Rig© Kirke King/ U.S. Fish and Wildlife Service

Each year, humans extract more than 6 Pg of organic carbon from the Earth’s crust (oil, coal, and natural gas) and convert it to CO2 that is added to atmosphere.

We have made no counter-balancing changes to remove CO2

from the atmosphere.

Golden Gate Bridge2000, Albert P. Bekker © California Academy of Sciences

Humans remove organic carbon from the Earth’s crust at a rate more than 100 times greater than the storage of organic carbon in newly-formed marine sediments.

Trajectory of Global Fossil Fuel Emissions

Raupach et al. 2007, PNAS

Recent emissions

1990 1995 2000 2005 2010

CO

2 E

mis

sion

s (G

tC y

-1)

5

6

7

8

9

10Actual emissions: CDIACActual emissions: EIA450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2

1850 1900 1950 2000 2050 2100

CO

2 E

mis

sion

s (G

tC y

-1)

0

5

10

15

20

25

30Actual emissions: CDIAC450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2

SRES (2000) growth rates in % y -1 for 2000-2010:

A1B: 2.42 A1FI: 2.71A1T: 1.63A2: 2.13B1: 1.79B2: 1.61

Observed

2000-2006 3.3%

20062005

2005 20062005

2006