Earth System Science. A highly interdisciplinary field the scientific basis for many key decisions and policy issues human society faces.

Transcription

1 Earth System Science A highly interdisciplinary field the scientific basis for many key decisions and policy issues human society faces. from: Johnson, Ruzek, Kalb, 2000 "Earth System Science and the Internet", Computers and Geosciences.

2 The Earth System Can be thought of interlocking sum of four components: Atmosphere Lithosphere (solid earth) Hydrosphere Ecosphere (or biosphere )

3 Global Environment

4 An introduction to studying change PROBLEM: How can you Understand a given issue, that is the result of interplay between these spheres?

5 An introduction to studying change Part 1: Some Basic Concepts

6 1) Time Scale is critical Consider: Weather vs. Climate What is the difference? Examples of weather? Examples of climate?

7 Or: Time point vs. running average Climate is what you expect.. But weather is what you GET.

8 Timescales and Humans Severe storms, tornadoes, etc: 0-100K people affected; hours. Day-to-day variations in weather: 0-100M people affected; days to weeks. Climate and global change: Billions affected; years, decades, centuries.

9 2) Systems System definition (most basic): A group of components that interact Further: components are linked together by Feedbacks = Selfperpetuating mechanisms of change (subject of next lecture)

10 Climate system We will often refer to the Climate System Can you speculate on some components of the climate system?

11 Climate System Components Ocean Solid Earth (Lithosphere) Hydrosphere (all water- ) Cyrosphere (snow/ice) Biosphere

12 The Climate System The Challenge: How do the system components interact to create climate?

13 Examples of interactions Ocean and atm. exchange heat, moisture and gases. Ocean is forced by atm. winds. Atm. is strongly influenced by land Ocean strongly influenced by bathymetry. Biosphere and solid earth processes control atmospheric composition. Cryosphere exerts a strong control on surface radiation balance.

14 3) Change vs. Variability A key concept (and issue!) in studying earth today. Think back to weather and climate Two key components: B) ANTHROPGENIC vs. NATURAL B) TIMESCALE

15 Climate Change vs Climate VariabilityV What do we mean by this? What are sources of natural climate variability? vs. Sources of human-induced climate change?

16 A) Natural vs. Anthropogenic Sources of Climate and Global Change Natural Variability Solar variability Volcanic activity Biological evolution El Nino Southern Oscillation North Atlantic Oscillation Human Activities Population growth Energy use Land practices Industrial activity Large-Scale Ecosystem alterations

17 The Systems Approach Consider the earth climate system as a whole and consider the interactions between the components. Study: How do the climate system components interact? Consider also climate system response to internal and external forcings (natural and human-induced).

18 The Climate System How do the system components interact? Consider also climate system response to internal and external forcings (natural and humaninduced).

19 Forcings * Forcing : an internal or external influence that causes as system to change or react * Often, system forcings are natural, and have their own cycles.

20 Internal forcing: e.g. greenhouse gas emissions External forcing: e.g. solar variations

21 B) Time Scale of Forcing Forcings can be broken down into short vs. long time scales Short : typically anthropogenic Long : natural only So..what is short and what is long? (clearly a bit subjective..)

22 Examples of Short Term Forcings Increase in atmospheric greenhouse gas concentrations. Introduction of ozone destroying chemicals into stratosphere. Deforestation and loss of biodiversity.

23 Greenhouse Gas Forcing What is the greenhouse effect? Can you name some powerful greenhouse gases?

24 The Keeling curve

25 Land clearing in N.Am began.

26 An Effect of climate forcing Global Temperatures

27 Vostok Ice Core Data 400K BP

28 Long-term Climate Forcings Orbital variations (predictable) Asteroid and comet impacts (unpredictable) Solar variations (semi-predictable?)

29 Snowball Earth Asteroid Impact? Snowball Earth

30 Orbital Changes Milankovitch Cycles : resultant combination of natural variation in several orbital parameters Time scales of 20-40,000 yrs Highly predictable Explains recent (pleistocene) glaciation cycles very well.

31 Orbital variations

32 Asteroid and Comet Impacts Clearly rather unpredictable.. (just ask any dinosaur in your neighborhood)

33 Asteroid Impact- Dinosaur Extinction.

34 The K-T boundary (K=Cretaceous; T=Tertiary)

35 Solar Variations The Sun has increased in intensity by about 30% since the formation of the earth 4.6 billion years ago.

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37 Climate Change or Climate Variability? A very important question, but often not easy to answer!

38 Must look at variations in context of past variation

39 Non-human ~100,000 yrs Time frames: often the key context you need to fully understand natural variability! ~20,000 yrs ~1000 yrs But how do you go back in time?

40 Summary To understand the current earth climate and possible future change, we must consider the earth s climate in the past. Past climate shows us the relative importance of interactions between the components of the climate system, AND the resilience of climate to perturbations, both natural and human-induced (anthropogenic).

41 END