Climate Change Our Present State of Understanding

Climate Change

Our Present State of Understanding

Jelte Harnmeijer

NASA Astrobiology Institute

&

Department of Earth and Space Sciences

University of Washington

(former affiliation)}

Humboldt State University06 April MMX

What’s in a name?

‘Greenhouse effect’

What’s in a name?

‘Greenhouse effect’

‘Global warming’

What’s in a name?

‘Greenhouse effect’

‘Global warming’

‘Climate change’

What’s in a name?

‘Greenhouse effect’

‘Global warming’

‘Climate change’

‘Global climate destabilization’

climate, n. The characteristic weather conditions of a country or region; the prevalent pattern of weather in a region throughout the year, in respect of variation of temperature, humidity, precipitation, wind, etc., esp. as these affect human, animal, or plant life.

What’s in a name?

The People

Science

Policy

What’s in a name?

The People

Science

Policy

What’s in a name?

The People

Science

PolicyMedia

Corporations

Climate change is real ...

IPCC (2007)

Climate change is real ...

IPCC (2007)

Gruber & Galloway (2009)

... and humans are to blame

IPCC (2007)

... and humans are to blame

• Temperatures are increasing

• Heat waves are increasing

• Heavy precipitation events are increasing

• Snow cover is diminishing

• Weather is becoming less ‘climate-like’:

o Less predictability

o Greater amplitude variations with higher frequency

The Atmosphere Subsystem

Secular changes do not pose the primary threat

How will greenhouse gas emissions trend?

(1) Hydrocarbon demand, supply & availability

ITPOES (2010)

How will greenhouse gas emissions trend?

(1) Hydrocarbon demand, supply & availability

How will greenhouse gas emissions trend?

(2) Population

How will greenhouse gas emissions trend?

(2) Population

• ~9 billion people predicted by 2050

• China’s population has stabilized

• ~ +750 million in India

• Most newcomers in sub-Saharan Africa

How will greenhouse gas emissions trend?

(3) Industrialization / ‘Development’

How will greenhouse gas emissions trend?

(3) Industrialization / ‘Development’

• Developing countries currently provide almost half of the world’s primary commodity exports, whilst importing less than a third.

• Industrializing today’s ~5 billion un-industrialized people and the net 3 billion newcomers would entail ~sextupling primary commodity output

Geological context

Zachos (2009)

Geological context

• Anthropocene CO2 concentrations *not* unprecedented

• Anthropocene temperatures *not* unprecedented

• But pace of change is paramount

• Great future unknowns:

o N2O

o CH4

o ocean structure & circulation

o cloud behaviour

Geological context

Positive feedback mechanisms accelerate change

Examples:

• Ice-albedo feedback

• Carbonate dissolution-ocean acidification

Geological context

Negative feedback mechanisms limit change

Examples:

• Calc-silicate feedback cycle

The Ocean Subsystem

• In contrast to our atmosphere, our oceans equilibrate slowly

• Timescale of 103 - 104 years typical

• Over the coming centuries, physicochemical response of our oceans will strongly control climate

• Marine biogeochemical cycling regulates key greenhouse gases

The Ocean Subsystem

Our oceans have absorbed ~1/3 of anthropogenic CO2 ...

CO2 flux [moles m-2 year-1]

The Ocean Subsystem

Our oceans have absorbed ~1/3 of anthropogenic CO2 ...

... but there is a price to pay:

pH ≈ - log10 [H+]

The Ocean Subsystem

Our oceans have absorbed ~1/3 of anthropogenic CO2 ...

... but there is a price to pay:

Some CO2 dissolves: CO2 (g) = H2CO3 (aq)

Which produces acidity: H2CO3 (aq) = H+ (aq) + HCO3

-

(aq)

Which dissolves carbonate:CaCO3 + 2H+ (aq) = Ca2+

(aq) + H2O + CO2

Which produces more CO2 ...

pH ≈ - log10 [H+]

The Ocean SubsystemImplicated carbonate biosynthesizers:

• Coccolithophores

• Cnideria

(coral reefs, ...)

• Foraminifera

• Echinoderms

(starfish, sea urchins, ...)

• Crustaceans

(crab, lobster, shrimp, crayfish, krill, barnacles, ...)

• Molluscs

(bivalves, ...)

The Ocean Subsystem

Stramma et al. (2008)

The Ocean Subsystem

Stramma et al. (2008)

The Ocean Subsystem

• Temperatures are increasing

• pH is decreasing

• Oxygen Minimum Zones are expanding

• Intense tropical cyclone activity is increasing

• Sea level is rising

Thinking ahead

Prevent?

or

Adapt?

Thinking ahead

hope, n. – Gr.: ελπίς (elpis)

Thinking ahead

“anticipation of misfortune”

hope, n. – Gr.: ελπίς (elpis)

Thinking ahead

IPCC (2007)

IPCC (2007)

Thinking ahead

Thinking ahead

Hawking (2007)

“... the worst case scenario is that Earth

would become like its sister planet, Venus.”

Thinking ahead

Planet Venus Earth

Density [g/cm3] 5.24 5.52

Radius [km] 6052 6378

Mass [·1024 kg] 4.86 5.97

Sidereal Orbit Period [Earth years] 0.62 1.00

Sidereal Rotation Period [Earth days] 243 1.00

Surface temperature [K] 730 288-293

Major atmospheric constituentsCO2, N2

N2, O2

Distance from Sun [A.U.] 0.72 1.00

Thinking ahead

Thinking ahead

Lovelock (2005)

Thinking ahead

Prevent?

or

Adapt?

(Coping not an option)

Thinking ahead

Solomon (2009)

Post-hydrocarbon

decay will be

slow

http://www.realfuture.org

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