An Overview of the Climate System
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CCAFS workshop titled "Using Climate Scenarios and Analogues for Designing Adaptation Strategies in Agriculture," 19-23 September in Kathmandu, Nepal.

CCAFS workshop titled "Using Climate Scenarios and Analogues for Designing Adaptation Strategies in Agriculture," 19-23 September in Kathmandu, Nepal.

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An Overview of the Climate System An Overview of the Climate System Presentation Transcript

  • An Overview of the Climate System Chris Lennard Climate Systems Climate Systems Analysis Group Analysis Group Contents of this module Contents of this module Energy Energy The Sun The Sun Energy imbalance Energy imbalance Continents Continents Turning earth Turning earth Coliolis Coliolis Large scale circulations Large scale circulations Radiation budget Radiation budget Greenhouse effect Greenhouse effect Variability Seasonal Inter-annual (ENSO, SAM, NAO, Volcanic) Decadal Climate Systems Climate Systems Analysis Group Analysis Group
  • Contents of this module Why do we have weather at all? Energy The Sun Energy imbalance Continents Turning earth Coliolis Large scale circulations Radiation budget Greenhouse effect Variability Seasonal Inter-annual (ENSO, SAM, NAO, Volcanic) Decadal Climate Change Weather and Climate Scales of our decision space Climate Systems Climate Systems Analysis Group Analysis Group Why do we have weather at all? Why do we have weather at all?An active sun.... Incoming solar radiation; Differential heating of the globe Climate Systems Climate Systems Analysis Group Analysis Group
  • Why do we have weather at all? Why do we have weather at all?Incoming solar radiation; 1. Differential heating of theDifferential heating of the globe globe results in energy transfer which together with 2. the spin of the earth and 3. position of the continents gives rise to our weather systems as we know them. Climate Systems Climate Systems Analysis Group Analysis Group Why do we have weather at all? Large Scale Circulations1. Differential heating of the  Tropics characterized byglobe results in energy transfer rising air and convectionwhich together with2. the spin of the earth and3. position of the continents  Sub-tropics characterized bygives rise to our weather descending air (dry)systems as we know them. If energy were not redistributed in this way the Equator would be about 14 degrees Mid-latitudes are high energy hotter and the Poles about 25 degrees zones (frontal systems) colder!! Climate Systems Climate Systems Analysis Group Analysis Group
  • Looking more closely....radiation Looking more closely....radiationIncoming radiation directly from the sun is 1370 W/m2 Interacts with the earth’s atmosphereAveraged over the whole earth is 342 W/m2 Different gases and particles absorb, reflect and re- radiate radiation at different wave lengths High clouds and aerosols reflect short wave radiation back to space cooling the earth 342 W/m2 1370 W/m2 Low clouds, water vapor and other green house gases absorb and re-radiate infrared radiation near Climate Systems Climate Systems Analysis Group Analysis Group Looking more closely....radiation The greenhouse effect.... Climate Systems Climate Systems Analysis Group Analysis Group
  • The greenhouse effect.... The greenhouse effect.... The Greenhouse effect keeps the earth warmer than it The Greenhouse effect keeps the earth warmer than it would be if it did not have an atmosphere. would be if it did not have an atmosphere. The surface of the Earths surface receives nearly twice as much energy from the atmosphere as it does from the Sun. Climate Systems Climate Systems Analysis Group Analysis Group The greenhouse effect.... The greenhouse effect.... The Greenhouse effect keeps the earth warmer than it The Greenhouse effect keeps the earth warmer than it would be if it did not have an atmosphere. would be if it did not have an atmosphere.The surface of the Earths surface receives nearly twice as The surface of the Earths surface receives nearly twice as much energy from the atmosphere as it does from the much energy from the atmosphere as it does from the Sun. Sun.In the absence of an atmosphere the Earth would average In the absence of an atmosphere the Earth would average about 30 degrees Celsius lower than it does at present. about 30 degrees Celsius lower than it does at present. Life (as we now know it) could not exist! Climate Systems Climate Systems Analysis Group Analysis Group
  • So we have this situation... Notice the Variation in the system Variability in the climate system occurs at a number of scales in Time (minutes to millennia) & Space (meters to 1000s km) The earth systems Natural Variability Notice: 1. Scales 2. Variability Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilityStart with one we all know – Seasonality Seasonal cycle SeasonalSpring Summer cycle is the largest single source of variability (besidesAutumn Winter diurnal) and a dominant driver of human activities and adaptations http://geography.uoregon.edu/envchange/clim_animations/ Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilitySeasonal cycle Seasonal cycle - MonsoonsResults from the oscillating tilt of the earth It is most often applied to the seasonal reversals of the wind directionLatitude of most intense heating moves north and southTropical variability tied to Inter-tropical Convergence Zone(ITCZ) which moves north and south – bi-modal seasonsSub-tropical variability linked to the descending high pressurecell variationsMid-latitude variability linked to the north-south shift of mid-latitude frontal systems Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilitySeasonal cycle – Monsoons Modifying the seasons: Intra- and Inter- Seasonal variation Longer time period (3 – 10+ years) variability often linked to slower changing ocean oscillationsMonsoons include  El-Ninõ Southern Oscillation (ENSO)almost all of the Westphenomena associated African  Southern African Mode (SAM)with the annual weather Monsooncycle within the tropical  Indian Ocean Dipole (IOD)and subtropicalcontinents of Asia,  North Atlantic Oscillation (NAO)Australia and Africa andthe adjacent seas and  Volcanic eruptionsoceans. East  Solar cycle Asian Monsoon  Decadal and longer........ Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilityIntra Seasonal variation - El Nino and La Nina (3-6 years) Intra Seasonal variation - El Nino and La Nina (3-6 years) Nino 3 region SST anomalies Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilityIntra Seasonal variation - El Nino and La Nina (3-6 years) Intra Seasonal variation - El Nino and La Nina (3-6 years) Nino 3 region SST anomalies Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilityIntra Seasonal variation - El Nino and La Nina (3-6 years) Intra Seasonal variation – Southern Annular Mode (weeks - years) Difference in the zonal mean sea-level pressure between 40oS and 65oS. Annular pattern with a large low pressure anomaly centred on the South Pole and a ring of high pressure anomalies at mid-latitudes. This positive phase → stronger westerlies around 55oS when SAM index is high. Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilityIntra Seasonal variation – Southern Annular Mode (weeks - years) Intra Seasonal variation – North Atlantic OscillationDue to the southward shift of the storm track, a high SAM index is associated The NAO index: the anomaly in pressure difference between the polar lowwith and the subtropical high in the boreal winter season (Lisbon and Iceland).  Anomalously dry conditions over southern South America, New Zealand and Tasmania A positive NAO means a more pronounced low over Iceland and high over the  Wet conditions over much of Australia and South Africa. Azores. The larger gradient leads to more and stronger storms on a more  Associated with warming trends over Antarctic peninsula, Argentina, northerly track and to warm and wet winters in Northern Europe. Tasmania and the south of New Zealand in summer and autumn. The SAM has shown a significant upward trend over the past 50 years, particularly in austral summer. Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilityInter Annual variation – Observed variability with multiple year Inter Annual variation – Indian Ocean Dipole (4-6 years) cycles Positive phase Warmer average sea-surface temperatures and greater precipitation in the western Indian Ocean region, with a corresponding cooling of waters in the eastern Indian Ocean. Tends to cause droughts in adjacent land areas of Indonesia and Australia and heavy rainfall over east Africa. Negative phase Opposite conditions with warmer water and greater precipitation in the eastern Indian Ocean, and cooler and drier conditions in effected African regions. Affects the strength of monsoons over the Indian subcontinent - often negates ENSO effect so ‘-’ phase IOD and El Nino = no drought. Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilityInter Annual variation – Solar cycle (sun spots) Inter Annual variation – Solar cycle (~ 11-12 years) Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilityInter Annual variation – Solar cycle (sun spots) Longer time scales: Decadal and Inter decadal variation These cycles affect/influence the shorter time scale cycles More difficult to observe and characterize as a results of poorer observational records the further we go back in time How they influence the shorter time scale cycles is often not well understood Termed - “Low frequency variability” Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilityPacific Decadal Oscillation (15-30 years) Atlantic multi-decadal oscillation (70 year cycle)During a "warm", or "positive",  Principle expression in the sea surface temperature (SST) field in thephase, the west Pacific becomes cool North Atlantic.and part of the eastern ocean warms  Effects temperatures and rainfall over much of the Northern Hemisphere (North America, Europe, North Eastern Brazil, African Sahel).During a "cool" or "negative" phase,  Associated with changes in the frequency of North American droughtsthe opposite pattern occurs. and is reflected in the frequency of severe Atlantic hurricanes.  It alternately obscures and exaggerates the global increase inModulates ENSO....or does ENSO temperatures due to human-induced global warming.modulate it? Uncertain... Climate Systems Climate Systems Analysis Group Analysis Group
  • Scales of Natural Variability How does Climate Change fit in...? e < decad years to cycles - Shorter Shorter cycles - years to < decade Shorter cycles - years to < decade eks) al to we Short cycles (diurnal to weeks) Short cycles (diurn to weeks) cycles (diurnal ShortAmplitude Amplitude longer) eca des and Long cycles (d Long cycles (decades and longer) Long cycles (decades and longer) Time Time Climate Systems Climate Systems Analysis Group Analysis Group How does Climate Change fit in...? Some evidence...temperature EnhancedBack toRadiative GreenhouseForcing Effect Climate Systems Climate Systems Analysis Group Analysis Group
  • Some evidence...Rainfall, more difficult What about the Future? Temperature Climate Systems Climate Systems Analysis Group Analysis Group What about the Future? What about the Future? Rainfall Sea LevelHigh degree of uncertaintyPPT increases very likely in high latitudesPPT decreases very likely in most subtropical land regions Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilityIn summary....... Question....... There is a lot of natural variability in the earth-atmosphere-ocean system These occur on many time scales and they modulate each other Are you, in your particular sector, able to adapt to and/or cope with So climate change is constant..... and complex. natural variability inherent in the climate system? We do not understand the mechanisms of many of the natural oscillations Challenges: Are there cycles we have not discovered yet? How do we filter the effects of natural cycles in our weather from those effects caused by greenhouse gas emissions? How do these cycles change through an enhanced greenhouse effect? Climate Systems Climate Systems Analysis Group Analysis Group Weather WeatherClimate and weather Climate and weather The expression of climate variability is in the weather …....to this! It is important to understand the difference between weather and climate: Climate is what we expect, weather is what we get! So we move from this.... (average in space and time) Climate Systems Climate Systems Analysis Group Analysis Group
  • Weather WeatherRemembering the large scale set up... The effects of our weather... We live in this large scale climate and we experience its effects through our WEATHER!  Tropics characterized by rising air and convection (thunderstorms)  Sub-tropics characterized by descending air (dry) Mid-latitudes are high energy zones (frontal systems) Climate Systems Climate Systems Analysis Group Analysis Group Weather WeatherThe effects of our weather... The effects of our weather... Climate Systems Climate Systems Analysis Group Analysis Group
  • Weather WeatherThe effects of our weather... Aaaaaaahhhhhhh......... Climate Systems Climate Systems Analysis Group Analysis Group In summary How does this affect me? Energy from the Sun drives the system Large scale circulations set up by: Energy imbalance Continents Turning earth Radiation balance - Greenhouse effect Variability in the climate system Seasonal Inter-annual (ENSO, SAM, NAO, Volcanic) Decadal Which of these do/can we currently adapt to? Climate Change Past Evidence Future possibilities Living in the climate system - Weather Climate vs weather Climate Systems Climate Systems Analysis Group Analysis Group
  • How does this affect me? How does this affect me? We operate in decision spaces at different scales of variability We operate in decision spaces at different scales of variability Fill in the table and discuss what modes of variability you are exposed to in your sector and what decisions you are called to make based on these Met services Water adaptation Biodiversity Weather Intermediate Climate Short term (0-7days) Medium Term (6-9mths) Long Term (10-50yrs) Agriculture met services Irrigation engineers Real Time → Week Seasonal Forecasts Decadal Changes Type of Decision Soil engineer Remote sensing Coastal management Operational (Days to weeks) Agricultural expertise Water conservation Tactical (weeks to months) Climatologist Strategic (Years to decades) GUI development for CC info Climate Systems Climate Systems Analysis Group Analysis Group Natural Variability Natural VariabilityVery long cycles : Thousands of years (Milankovitch cycles) Very long cycles : Thousands of years (Milankovitch cycles) Eccentricity 100 000 years Currently the difference between closest approach to the Sun (perihelion) and furthest distance (aphelion) is http://www.sciencecourseware.org/eec/GlobalWarming/Tutorials/Milankovitch/ only 3.4% (5.1 million km). This difference amounts to about a 6.8% increase in incoming solar radiation (insolation). Perihelion presently occurs around January 3, while aphelion is around July 4. When the orbit is at its most highly elliptical, the amount of solar radiation at perihelion is about 23% greater than at aphelion. Climate Systems Climate Systems Analysis Group Analysis Group
  • Natural Variability Natural VariabilityVery long cycles : Thousands of years (Milankovitch cycles) Very long cycles : Thousands of years (Milankovitch cycles) Obliquity When the obliquity increases, the amplitude Precession When the axis is aligned so it points toward 41 000 years of the seasonal cycle in insolation 26 000 years the Sun during perihelion, one polar (23.44o) increases, with summers in both hemisphere will have a greater difference hemispheres receiving more energy from the between the seasons while the other Sun, and the winters less. hemisphere will have milder seasons. The hemisphere which is in summer at perihelion will receive much of the corresponding Lower obliquity favours ice ages both increase in solar radiation, but that same because of the mean energy from the sun is hemisphere will be in winter at aphelion and have a colder winter. The other hemisphere reduced in high latitudes (polar regions) as will have a relatively warmer winter and cooler well as the additional reduction in summer summer. insolation. Climate Systems Climate Systems Analysis Group Analysis Group Natural VariabilityVery long cycles : Thousands of years (Milankovitch cycles) Ice Ice Ice Ice Ice age age age age age At present, only precession is in the glacial mode, with tilt and eccentricity not favourable to glaciation Climate Systems Analysis Group