Climate

Question 1

Useful text

Answer 1

Barry and Chorley (1992) - Atmosphere, Weather and Climate

Question 2

IPCC (2018)

Answer 2

Must keep Global Warming below 1.5 degrees

Question 3

Ships et al (2016)

Answer 3

• last 150 years CO2 driving temp increase
• GHGs = main cause drivers recent warming
• contribution natural forcing (solar, volcanism) to long-term trend are insignificant
• Anthropogenic forcing varies hemispheres
• Paleoclimate time scales (1mn years ago ice core records) cause-effect direction reversed - temp chances cause CO2/ CH4 changes

Question 4

Cryosphere Changes

Answer 4

2002 Larsen Ice Shelf Collapse (Arctic)

• Break up ice sheet 1.5x size UK
• Albedo - exposure huge area ocean = huge impact local and regional energy balance = implications ocean climate and atmosphere

Question 5

Lithosphere Determines Climate

Answer 5

Mount Pinatubo - plume ash and sulphate particles - impact energy balance and thus temp - 1992/3 average temp N hemisphere reduced 0.5-0.6 degrees, entire planet cooled 0.4-0.5 degrees
- 1816 Mt Tambora - year w/o a summer - problem starvation

Question 6

Holden (2012)

Answer 6

• energy and entropy
• sensible heat (raise temp) latent heat (evaporation)
• global radiation = sum short-wave radiation received directly and indirectly (diffused)
• albedo
• net radiation = difference total incoming and outgoing radiation
• Bowen ratio (sensible heat flux divided latent heat flux)- degree of wetness surface control surface temp
• global energy balance
• hydrosphere
• global precipitation / evaporation approximate equal - not regionally
• evaporation from land = transpiration (vegetation controlled), interception loss (depends vegetation and atmosphere) and soil surface evaporation
• drought - def depend local climate
• atmospheric circulation driven by excess solar radiation tropics compared polar - Hadley cell - polar cell - between these two cells = reverse cell w sinking air 30 degrees N/S - ferrel
• easterly winds or trade winds meet near equator - ITCZ
• geostrophic wind
• ferrel cell schematic - mid-latitudes disturbed - cyclones and rossby waves
• coriolis - winds deflection to right N and left S
• within rossby waves = fast bands air or jet streams - subtropical westerly jet streams 30 degree N/S - boundaries hadley cells
  mid/high latitudes
• westerly polar front jet stream (not fixed location) - thermal wind related thermal gradient created by temp difference polar and tropical air where two air masses meet at polar front
• interaction air masses determine weather m/h latitudes
• upper-level divergence + zone ascending air = cyclogenesis vs upper-level convergence and zone subsiding air = anticyclogenesis
• fronts in general air rise and precipitation
• occluded front = cold front overtakes warm front
  oceans
• much oxygen breathe produced phytoplankton oceans
• Dead Sea (saltiest lake world, 25% denser normal sea water, between Jordan and Israel, Middle East water shortage, shrinking 1m year)
• coriolis, gulf stream (North Atlantic subtropical gyres 30 N/S), thermohaline, North Atlantic Deep Water (NADW)
• sinking water must balanced upwelling - often somewhere else globe - upwelling regions lots nutrients, bloom phytoplankton and fishing - eg. Peru coast (el nino warmth)
• contest over the Arctic for fossil fuels + sea routes
• North Atlantic Europe warmer winter
  Walker Circulation, El Nino Southern Oscillation + North Atlantic Oscillation
• Walker circulation - rising air Indonesian Archipelago and sinking air eastern Pacific - wet humid climates IA and coastal deserts Peru - east-west - closely coupled to sea surface temp pacific (cool water east, warm west) - Pacific Ocean south america cold air too stable Hadley cell so flows westwards to west pacific where heated so can ascend
• El Nino Southern Oscillation - exchange air south-east pacific high and Indonesian equatorial low - la nina or normal = trade winds intense and converge warm regions west pacific = Australia + Indonesia rain (COLD pacific east and atmosphere S America) - then every few years el nino = trade winds relax, precipitation and warmth shifts east = drought Indonesia, South America heavy rain
• North Atlantic Oscillation -changes strength ocean surface westerlies - Azores and Iceland atmosphere pressure difference - high NAO index = Icelandic low pressure strong = increases influence cold Arctic air masses NE N America and enhances westerlies carrying warmer air masses E Europe - low index = slow blocking anticyclones N Atlantic / NW Europe (cause dry summer, cold winters)

Question 7

Goosse et al (2010)

Answer 7

• climate = mean weather over 30 year period (but must look longer periods eg. if considering last glacial max)
• climate system = interactions atmosphere, hydrosphere, cryosphere, land surface, biosphere
• ATMOSPHERE = 78% nitrogen, 21% oxygen
• pressure and lapse rate (neg lapse rate = temp increase height or temp inversion = stable vs pos lapse rate = less stable) links to troposphere (temp decrease), stratosphere (temp up, ozone), mesosphere (td), thermosphere (tu)
• Hadley cells - move air from equator to poles - surplus to deficit heat - would go to poles but limited to 30 degree latitude - northern boundary tropospheric jets (strong westerly winds) - coriolis effect at surface gives rise to easterly trade winds (tropics) - ferrel cell tropics - N hemisphere winds clockwise around high pressure and anticlockwise around low pressure - opposite S - ITCZ and monsoons
• link climate temp and precipitation eg. ITCZ lot precipitation, deserts, monsoon (winter dry air little rain vs summer moist air lot rain - topographically induced eg. Himalaya)
• OCEANS - density sea water increases with salinity and pressure / decreases higher temp - currents driven winds eg. mid-latitude westerlies = east ocean currents and trade winds = west currents tropics
• Ekman transport - due earth’s rotation, ocean transport induced wind is perpendicular to wind stress (right N hemisphere, left S)
• deep ocean convection occur high latitudes (low temp, high salinity = sink water) - North Atlantic Deep Water eg. - water upwells different ocean basin - THERMOHALINE
• salinity influenced freshwater fluxes
• CRYOSPHERE - water in solid form - permafrost, Greenland and Antarctic ice sheets - high albedo = climatic impact - ice sheets and sea level
• LAND SURFACE / BIOSPHERE - topography (mountains), distance to coast, vegetation type influences climate eg. albedo (vegetation lower albedo than soil - deserts higher albedo) - water storage by vegetation (hydrological cycle) - EVT, carbon cycle - biomes (Desert, grassland, scrubland, woodland, forest) - feedbacks

Question 8

Baede et al (2001)

Third IPCC Working Group I Assessment Report

Answer 8

• weather = fluctuating state atmosphere vs climate = average weather (climate change = variations of mean)
• human induced CC hard to predict
• need understand the whole climate system (5 linking components + external forcing eg. sun, volcanoes, humans) to understand climate change
• GHGs absorb infrared radiation from earth = increase earth’s surface temp - also ozone layer role
• ocean regulator climate (thermohaline)
• cryosphere - albedo + driver deep ocean circulation (ice sheets and sea level variation)
• vegetation and soils (land surface) control how energy received from sun is returned to the atmosphere - long-wave, evaporation etc. - land surface roughness and wind - types organism and carbon amounts photosynthesis and storage
• sun and earth’s energy balance + natural greenhouse effect for a habitable temp
• system response to external forcing variations varies spatially and temporally - equally internal variations = natural climate variations (feedbacks also! - pos + neg)
• Radiative Forcing = difference between insolation absorbed by Earth and energy radiated back space - climate forcings = influences changing climate by altering RF - pos RF = absorb more, warming - neg = loos, cooling
• complex, non-linear system (climate)
• climate fluctuates - G/IG - Little Ice Age etc
• regional cimate - ENSO, el nino, la niña - North Atlantic Oscillation impact Europe (Iceland low pressure and Azores high pressure - cyclones to Europe)
• human impacts - CO2, CFCs and ozone, land use change - industrial rev worse impact from - impact radiative forcing - enhanced greenhouse effect - aerosols neg RF
• climate models - need coupling eg. atmosphere and ocean circulations can be difficult to achieve - predict future by comparing present or past - IPCC emissions scenarios - not predictable entirely - rapid change may occur eg. reorganisation thermohaline
• glacier retreat, sea level rise 10 - 20cm C20th - warming - weather regional changes eg. drier mediterranean, more rain mid / high latitudes - uncertainty how much human vs natural variability

Question 9

Petersen et al (2014)

Answer 9

• Winds named by direction come from
• Winds always blow high to low pressure at surface
• Wind speed function gradient of air pressure between high / low pressure systems (pressure gradient force - high = close isobars = fast winds)
• Coriolis force opposes PGF = wind deflected, not straight line (N hemisphere deflects right, S left) - Coriolis stronger towards poles and stronger w faster wind - coriolis only acts on air already in motion by PGF / only impacts direction not wind speed
• Centripetal acceleration (act on air flowing around circulation centres) also influence wind direction - force at right angles to flow wind and inward to centres of rotation = circular flow around centres high or low pressure - also friction acts
• air under influence PGF and Coriolis moves parallel to isobars where friction is low = geostrophic winds (PGF and C in balance)
• winds flow around high pressure (anticyclone) or low pressure (cyclone) centre = gradient wind - addition of centripetal force inwards
  Thermal Wind systems - sea and land breezes (day land heats = sea breeze vs night land cools faster = land breeze) - mountain (night, downslope wind) vs valley breeze (day, upslope air) - monsoons
• Three cell Model - equator warm, ITCZ (forms due solar and trade wind convergence) thermal low, draws air from subtropics, air reaches equator and rises to troposphere then flows horizontal N/S then coriolis force = deflection so by 30 degrees moving E/W (subtropical jet stream)
• northeast trades, southeast trades due coriolis - polar jet stream 60 degree N/S (subtropical westerlies collide here w cold air from poles = frontal uplift and mid-latitude cyclones)
• ITCZ shift (south equator Jan vs north in July = intense monsoon)
• polar jet stream forms by deflection upper air winds by coriolis - moves west to east - flow intense by temp / pressure gradient cold air poles meet warm air tropics - polar front = where these airs meet = mid-latitude cyclones form beneath jet stream troughs (frontal uplift)
• two air masses often meet mid latitudes = temp difference between them intensified = front - boundary always up over cold air (denser) = frontal uplifting = precipitation
• cold front = advancing cold dry air mass displaces warm unstable one - SE to E
• warm front = advancing warm moist air mass replaces retreating cold one - NE direction
• occluded front = fast cold front overtakes slow warm front - cold occluded front if air behind front colder air ahead and warm if air behind front warmer than air ahead
• thunderstorms form when moist, unstable air lifted vertically - air cools, reaches dew point = condensation + cloud - continued uplift then = storm
• air mass storm - can get severe presence mid-latitude cyclone providing energy
• tornadoes - EG Oklahoma 1999 - receives most tornadoes, esp May when warm moist air from Gulf Mexico interacts with NW cold fronts - 250 buildings destroyed, 7500 damaged, $1.2bn damage, 40 deaths (warning systems)
• ITCZ + subtropical high-pressure zone (descending airflow)
• hurricanes = cyclonic storms over tropics - centre = low pressure (eye descending air, clear skies)
• hurricanes need oceans 26.5 degrees + 200m deep - need supply warm air - storm gets more energy and moisture to become hurricane - dissipate when latent heat energy available reduced enough (land or cooler seas)
• Bhola cyclone - Bangladesh Nov 1970 - 300,000 died (unprepared)
• El nino = occasional warm ocean surface waters Peru - usual upwelling reduced - formation linked souther oscillation - normally surface low pressure develops in N Australia / Indonesia and high pressure Peru coast = trade winds Pacific east to west (easterly flow brings warm water west = A/I storms + Peru cold upwellings to replace warm water) - but el nino year = weak high pressure west - trade winds reduced = west to east flows = warmth Peru = drought west, rain S America, Pacific hurricanes - sometimes get la nina = trade winds v strong = abnormal accumulation cold water east Pacific = heavy monsoons India/ SE Asia, wet weather SE Africa, wet Australia, cold Canada / US etc

Question 10

Charlson, Lovelock, Andreae and Warren

Answer 10

CLAW hypothesis

• proposal neg feedback loop between ocean ecosystems and climate
• The hypothesis specifically proposes that particular phytoplankton that produce dimethyl sulfide are responsive to variations in climate forcing, and that these responses act to stabilise the temperature of the Earth’s atmosphere.

Question 11

McGregor and Ebi (2018)

ENSO

Answer 11

• climatic variability connected with atmosphere and ocean variations and land surface properties
• need understand climate variability to understand links with health and pos health risks of climate change
• El Nino Southern Oscillation (ENSO) linked to climate variance and impact health (land and ocean temp / precipitation extremes, ecosystem health, drought, flooding etc)
• ENSO = variations as result variations sea surface temp / atmospheric pressures tropical Pacific Ocean - el nino (ocean) + southern oscillation (atmosphere component)
• variety 2-7 years ENSO can be problematic for impacts
• indices eg. SOI (pressure difference Tahiti and Darwin) - also equatorial SOI (eastern Pacific and Indonesia) but less long records
• Stefan-Boltzman Law = cooler object, lower long wave radiation amount emitted
• monitored through sea surface temp (as ocean-atmosphere interaction)
• blended index eg Multivariate ENSO Index (MEI) - 6 variables ocean/atmosphere recorded over tropical Pacific
• 2015/16 El nino event = forest fires Indonesia, floods Peru, coral bleaching, health issues - need see how CC impact - also la nina bad eg. 1998/9 flooding Bangladesh, Venezuela and China - believe el nina/ la nina are natural variabilities climate - but will intensity / frequency change with CC (some modelling evidence for increased frequency ENSO events with global warming but unsure if weaker / stronger)

Question 12

Mayes and Wheeler (2013)

British Climate

Answer 12

• British Isles weather / climate = products polar and tropical air conflict - regional contrasts - contrasting air masses = temp fluctuations and rainfall
• polar jet stream N GB = path mid-latitude westerlies
• North Atlantic Oscillation - positive = rain and enhanced wind risk - neg = blocking anticyclones NW Europe / NE Atlantic
• topography

Question 13

Clark et al (2016)

Answer 13

• policy debate CC needs stop focusing small time window as it obscures many problems CC - need think long-term in terms of past and future - emphasis on change by 2100 is not helpful in focusing long-term policy commitments
• lag times - carbon will in atmosphere long past this
• need complete decarbonisation of world’s energy systems
• IPCC focus 2100
• 20-50% anthropogenic CO2 emissions released next 100 years remains atmosphere at year 3000 - 100% sea level rise any emission scenario remains after 10,000 yrs
• context of palaeoclimate record - 20,000 years back perspective + 100,000 years forward
• lag sea level rise behind temp forcing - thermal expansion, glaciers (antarctic - 58m sl rise - and Greenland - 7m sl rise) - SL next 10,000 yrs - far exceed IPCC predictions based 2100 (regional SL differences) - next 2000 yrs 25-36 countries lose at least 10% land sl rise
• lags mean already done damage - need net zero emissions
• decisions now huge implications