Transcript What do we KNOW

Biomolecules tell us about how climate
changed in the past... and how it might
change in the future
Rich Pancost, The School of Chemistry
Outline
• A bit about global warming…
• What can the past tell us
– First, how I study the past
• Biological compounds are diverse and some compounds –
particularly lipids – can be robust tracers of environmental
processes
• Analytical chemistry (i.e. CSI science) underpins this research
– Studying a global warming event in the past
Global Warming
How should we talk about climate change?
• What do we know?
• What do we probably know?
• What do we think?
• What do we have no idea about?
How do we study climate change?
• We try to measure changes
How do we study climate change?
• We try to measure changes
• We make computer models of climate
How do we study climate change?
• We try to measure changes
• We make computer models of climate
• We study the past
What do we KNOW?
That Carbon Dioxide and Methane Concentrations in the
Atmosphere are Increasing
Data from Scripps CO2
Program.
What do we KNOW?
• CO2 concentrations are higher than they have been for 1000 yrs
But how do we know what CO2 was
before we could measure it?
Direct
measurement
INDUSTRIAL
REVOLUTION
What do we KNOW?
• CO2 concentrations are higher than they have been for 650 kyr
What do we KNOW?
• CO2 concentrations are higher than they have been for 20
MILLION years
13C
versus 12C
8 million
40 million
Pagani et al., 2005 Alkenone-derived pCO2 record
Summary
That carbon dioxide and methane concentrations are higher than
then at any time in the past 1 million years
We think that they are higher than at any time in the past 30 million
years (alkenone pCO2 proxy; Pagani et al., 2005)
We think that they are not at all close to the highest levels in Earth
history
We think that they are changing faster than at any time in Earth
history
What do we KNOW
• CO2 concentrations are increasing due to fossil fuel burning
• CH4 concentrations are probably increasing because of
–
–
–
–
–
Increased rice cultivation and ruminant animal agriculture
Natural gas pipeline leakage
Offset by wetland destruction
But also thawing of permafrost?
Increased production due to warmer/wetter climate?
• Other greenhouse gas concentrations are also increasing
– N2O
– CFCs
What do we KNOW? That higher CO2 will cause
ocean pH to decrease
H2CO3 + CO32+
Ca2+
H2O
+
CO2(aq) CaCO3(s)
Calcium Carbonate Dissolves
2HCO3-
What do we THINK? That lower pH will adversely
affect sealife
What do we KNOW? That higher CO2 will cause
temperature to increase.
What do we KNOW?
•
•
That elevated carbon dioxide WILL cause warming.
We are fairly certain that it has already caused warming
– 0.6°C temperature increase over the past century
– 3 hottest years on record are post-1998
– 19 of 20 occurred since 1980
Compiled by the Climatic
Research Unit of the
University of East Anglia
and the Hadley Centre of
the UK Meteorological
Office
What do we KNOW?
•
•
That elevated carbon dioxide WILL cause warming.
We are fairly certain that it has already caused warming
What do we THINK?
That elevated greenhouse gases WILL cause warming
of about 4C
What do we KNOW?
That elevated greenhouse gases WILL cause warming
That warming will cause
– Sea level rise
– Melting of glaciers
– Increased aridity in some places and wetter
conditions in others
– Increased likelihood of extreme weather events
– Warming will stress certain biomes
What do we THINK?
• That warming will cause sea level rise from thermal
expansion of the ocean and probably from melting
of glaciers
What do we KNOW?
• Warming will make some places drier and some
places wetter
What do we KNOW?
• There will be more hurricanes
So what is the debate all about?
•
How much will CO2 and CH4 levels increase?
– What are the sinks (the ocean, trees, soil)?
•
How much will temperature increase?
– What are the feedbacks?
•
How much will sea level rise?
– How do ice sheets respond to climate?
•
REGIONAL AND LOCAL EFFECTS
–
–
–
–
Will some countries be flooded or suffer drought?
How will that affect political stability in some regions?
Or biodiversity?
How will that affect global economics
What can we learn from the past?
Based on the Permo-Triassic
mass extinction event
270 Million years ago
Has catastrophic (rapid) methane release
occurred in the past?
What was its impact?
What do I do to study it??
Lipid structural variability
HH
HH
H
C
H
C
H
C
H
HH
C
H H
C
C
H H
C
H
O
OH
Lipid structural variability
O
Eucarya
OH
Animals
Flagellates
Plants
Microsporidia
Fungi
Ciliates
Slime moulds
Bacteria
Diplomonads
O
O
OH
O
HO
O
Green non-sulfur
bacteria
HO
Archaea
OH
O
OH
O
Thermotoga
Nitrospira
Cyanobacteria
Green sulfur
bacteria
X'
Sulfolobus
Gram positive
bacteria
HO
Pyrodictium
X
Methanobacterium
Pyrococcus
Thermoplasma
Archaeoglobus
Methanopyrus
Methanococcus
O
O
OH
O
O
OH
O
Thermoproteus
Halobacterium
What can carbon isotopes tell us?
More
13C
0‰
Carbonate
-8 ‰
CO2(aq)
98.9%
ep
d13C
values
1.11%
-22 ‰
Biomass
Kerogen
-26 ‰
12C
13C
Less
13C
Lipids
Methane
Biomarker Geochemistry is built on a foundation
of robust analytical chemistry
Aim: To isolate a complex extract containing hundreds of
compounds and separate it into discrete groupings of
compound class amenable to GC or LC analysis
Raw sample
GC sample
Sample Analytical Protocol
• Soxhlet
Eluent
• Ultrasonication
• Bligh-Dyer
Sample
• Liquid/liquid
extraction
Extraction
• Autoextraction
Total lipid extract
Residue
Chromatography
Neutral fraction
Acid fraction
Polar fraction
1
Appropriate Derivatisation
GC-FID
GC-MS
LC-MS
GC-C-IRMS
2
3
Analyses – Hyphenated Techniques
Gas Chromatograph
Py – Gas Chromatograph
Liquid Chromatograph
Flame Ionisation Detector
Mass Spectrometer
•
Combustion – Isotope Ratio Mass
Spectrometer
Thermal Conversion – Isotope
Ratio Mass Spectrometer
•
Relative Abundance
•
•
•
•
•
Retention Time
Long-Term Cenozoic Climate Change
Temperature
Adapted from Zachos et al., 2001
The Paleoene-Eocene Thermal Maximum
13C-depleted
carbon
Methane!
Zachos, James, Mark Pagani, Lisa Sloan, Ellen Thomas, and Katharina Billups (2001). "Trends, Rhythms,
and Aberrations in Global Climate 65 Ma to Present". Science 292 (5517): 686–693.
Questions:
1. What triggered the methane release?
2. How much methane was released?
3. When it became CO2, how much warming did
it cause?
4. What were the impacts on the climate,
environment and life?
Questions:
1. What triggered the methane release?
2. How much methane was released?
3. When it became CO2, how much warming
did it cause?
4. What were the impacts on the climate,
environment and life?
How much warming did it cause?
O
O
OH
O
HO
O
O
OH
O
O
OH
O
O
O
HO
O
OH
O
Zachos et al., 2006
Questions:
1. What triggered the methane release?
2. How much methane was released?
3. When it became CO2, how much warming did
it cause?
4. What were the impacts on the climate,
environment and life?
Changes in storms?
• Back to Tanzanian and New Zealand sites
• Lots of biomarkers from plants washed out to sea
• But how abundant are they?
29
Relative Intensity
Hydrocarbon Fraction
31
33
27
Standard
23
25
21
10
20
30
40
Retention Time
Changes in storms?
Abundance mg g-1
Average Chain Length
Fatty Acids
HMW fatty acids (Higher Plant)
d13C (‰)
-36
-34
-32
-30
-28
-26
0
1
2
3
4
22
23
24
25
26
27
5
10
O
Depth (m)
OH
15
O
OH
20
25
30
35
28
Conclusions: Implications for future
climate change?
• Global warming is an important concern, but we need to know
more
• Insight can come from studying the past
• This requires the application of good geological knowledge
but new approaches to study the chemistry of the rocks also
helps
• What have we learned about the PETM
–
–
–
–
There was a large release of greenhouse gases
This caused climate to warm by about 5C
This appears to have caused an increase in storms
But more dramatic changes – such as those discussed in the
article in The Independent – are not observed
• We must be cautious in how we use this approach…
The Cobham Lignite – a PETM terrestrial
setting (With D. Steart, M. Collinson and A. Scott, Royal
Holloway)
Collinson et al., 2001
The Cobham Lignite
Pancost, R. D., Steart, D. S., Handley, L., Collinson, M. E., Hooker, J., Scott, A. C.,
Grassineau, N. J., and Glasspool, I. J. (in press) Terrestrial Methanotrophy at the
Paleocene-Eocene Thermal Maximum. Nature.
The Cobham Lignite
Methanotrophs
Heterotrophs
Conclusions: The Larger Picture
• A wide variety of environmental processes can be studied using
lipids and similar biomarkers
– Modern:
• AOM in the ocean and methanogenesis in wetlands
• Petroleum (and other OM) degradation and preservation
• Role of OM in releasing arsenic into aquifers
• Extreme environments (geothermal springs)
– Ancient Extreme Events
• PETM
• Extinction events
• The change from a greenhouse climate to our current climate
• This requires the skilful application of state-of-the art analytical
chemistry techniques and instrumentation
Acknowledgements
• Ian Bull and Rob Berstan (and the NERC Life Sciences Mass
Spectrometry Facility)
• The EU for funding the METROL programme and an EST
grant (BIOTRACS) that supports A. Aquilina’s PhD
studentship
• The NERC for a grant to P. Pearson, R. Pancost and T. Elliott;
and for supporting L. Handley’s PhD Studentship
• Joyce Singano and all other members of the TDP
• The Leverhulme Trust for a grant to M. Collinson, R. Pancost
and A. Scott
• The NZ Marsden Fund for a grant to E. Crouch, H. Morgans
and R. Pancost