Emerging Strategic Research Theme

The Habitable Earth

Key themes

Causes of climate changeEcological effects of climate changeHabitable planet in a wider context

Sun KwokFaculty of Science

Why this theme?

• It is perhaps the major challenge scientists face in the 21st century and therefore of tremendous practical importance

• It is scientifically interesting

• Requires interdisciplinary approaches

• Demonstrated record of research excellence

Members• Causes of climate change

– Jonathan Aitchison– Jason Ali– Nathalie Goodkin– Z.H. Liu– G.C. Zhao

• Habitable planet in a wider context– Sun Kwok– Man Hoi Lee– Yiliang Li– Kono Lemke– Steve Pointing

• Ecological effects of climate change– David Dudgeon– Clement Dumont– Melissa Hart– Nancy Karraker– Leszek Karczmarski– Kenneth Leung– Vengatesen Rajan– David Thomson– Gray A. Williams– Rudolf Wu– Y.Q. Zong

Objectives

• To provide a sound and rigorous scientific basis for global change

• To understand the changing interactions between the physical and biological components of the Earth system

• To understand the ecological implications of climate change

Track record of the team (last 5 years)

• Science: 5• Nature: 4• Nature series: 3• Proceedings of the National Academy of Sciences: 3

median age of the team is: 43

High impact publications

Earth as an integrated system

• Atmosphere, hydrosphere, biosphere and geosphere

• Interacting physical, chemical and biological processes

• Human impacts (e.g., on habitat destruction, biodiversity loss, atmospheric and ocean composition)

Atmosphere

OceansBiosphere

Solid Earth

Earth as a System

Earth today

One of the greatest impact of NASA’s lunar program is the public appreciation of how fragile the Earth is

Climate Change: Past and Present

• Global climate evolution

• Plate tectonics-climate interaction

• Past atmospheric CO2

• Past Asian monsoon variability

• HK regional climate change

• Asian monsoon-El Nino interaction

34 M yr ago

Influences of assembly and breakup of supercontinents on hydrosphere, atmosphere and biosphere

The assembly of a supercontinent may cause:1. Decrease in total land areas2. Low-rate oceanic production3. Global sea level subsidence4. Decrease of CO2 in atmosphere5. Colder and dry weather - ‘Icehouse’ 6. Mass Extinction – P/T Boundary Event

The breakup of a supercontinent may cause:1. High-rate oceanic production2. Global sea level rise3. Increase of CO2 in atmosphere – continental/oceanic

rifting4. Warmer and wet weather - ‘greenhouse’ 5. Explosion of life – Cambrian explosion

Life and the Earth Environment• When did the Earth become habitable, and

why did life boom in the Cambrian period?

• How and when the Asian monsoon was generated?

• How has vegetation responded to climate change?

• Environmental changes in Hong Kong.

Impact of CO2 emissions

• Changes in atmospheric temperature leads to ocean circulation, ocean/atmosphere interactions, evaporation/precipitation patterns

• Can the oceans sustain their role as CO2 sinks?

Ecosystems and population processes

• Impact of environmental change on wildlife demography, population structure, population persistence, invasive species and other multi-species interactions (David Dudgeon, Gray Williams, David Thomson, Kenny Leung, Leszek Karczmarski, Clement Dumont, Nancy Karraker)

Effects on organisms• Individual effects of

environmental stress: thermal, chemical, osmotic, hypoxic, acidification (Rudolf Wu, Kenneth Leung, Rajan Vengatesan, Gray Williams, David Dudgeon)

Urbanization

• The urban heat island: analyses of spatial variability and exposure (Melissa Hart)

• Building energy consumption under a future warming climate (Melissa Hart)

Habitable planet in a wider context

• Life in extreme environments: understanding the environmental limits for life on Earth and how geochemical factors determine the limits of life

• Origin of life• Earth analogs: we cannot do experiments on

Earth. We need to learn from other examples in the Solar System.

Habitable Earth in the Wider Context

• Extreme environments on Earth as tractable analogs to inform the search for life on other planets. (Pointing, Li)

Polar desert, Earth Polar desert, Mars

Habitable Earth in the Wider Context• Synthesis, stability and concentration of biomolecules in extreme environments on early Earth (Lemke, Li)• The role of fluids in early life processes (Lemke, Li)

Habitable Earth in the Wider Context•How do microbes interact with geo-materials?

Bio-mineralization (Li)

Ni-Cr-Fe-C alloy identified from 1600 million years dolomite (Li unpublished data).

Habitable Earth in the Wider Context• How does evolution of the Solar System affect Earth’s Habitablity? (Lee)• Habitable worlds elsewhere in the Solar System and the Universe (Lee)• The delivery of pre-Solar System organics and their effects of the origin of life on Earth (Sun Kwok)

Extreme Environments

Deep OceanAtacama Desert, Chile

Permafrost Area

Grand Prismatic Spring (Yellowstone)

Acid Mine Drainage

SaltyLake

Summary

• There has been significant climate change over the history of the Earth due to internal and external perturbations

• The Earth is an integrated system

• Climate change is a complex subject requiring input from geology, chemistry, physics, biology, and astronomy