Climate Change - PowerPoint PPT Presentation

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Climate Change

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Cities tend to be hotter than the surrounding countryside. ... the cities were getting cooler relative to their surroundings rather than warmer. ... – PowerPoint PPT presentation

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Title: Climate Change


1
Climate Change
  • The 4-point consensus view of global warming
  • Some objections impartially considered
  • (Evaluating Impacts)

Nb this is my personal view, and I am speaking
in a personal capacity. This talk or something
like it is available from... http//www.wmconnolle
y.org.uk/sci/gw/
2
(1) Global Warming is happening...
http//en.wikipedia.org/wiki/ImageGIS_Global_1880
_2005.gif
3
(2) We're causing it
4
(2) We're causing it (cont...)
5
(2) ...we're causing it (...cont 2)
http//www.grida.no/climate/ipcc_tar/wg1/figspm-3.
htm
6
(3) It will get worse
http//www.grida.no/climate/ipcc_tar/wg1/figspm-5.
htm
7
(4) This will be a Bad Thing
  • Sea level rise is bad, but slow
  • Temperature rise regionally varying winners and
    losers, political tradeoffs
  • Ecological impacts important, but I don't know

8
Common myths, impartially considered
  • Satellite temperatures - show warming too
  • The urban heat island - negligible effect
  • The hockey stick controversy
  • The Day After Tomorrow - will not happen
  • Little relation between the Ozone hole and GW
  • CO2 increase is anthropogenic (more than...)

9
Satellite temperature measurements
  • Mears et al 0.193 C/decade
  • Spencer and Christy version 5.2, 0.123 C/decade
  • Fu et al, 0.2 C/decade (May 04)
  • Vinnikov and Grody, with 0.22C to 0.26C per
    decade (Oct. 03)
  • Surface record 0.06 C/decade over the past
    century and 0.15 C/decade since 1979.

http//www.ssmi.com/msu/msu_data_description.html
10
(No Transcript)
11
Urban Heat Island (1)
  • Cities tend to be hotter than the surrounding
    countryside. But (for the purposes of the
    temperature record) we care about trends ie are
    cities getting even warmer?
  • Hansen et al. (JGR, 2001) adjusted trends in
    urban stations around the world to match rural
    stations in their regions, in an effort to
    homogenise the temperature record. Of these
    adjustments, 42 warmed the urban trends which
    is to say that in 42 of cases, the cities were
    getting cooler relative to their surroundings
    rather than warmer. One reason is that urban
    areas are heterogeneous, and weather stations are
    often sited in "cool islands" - parks, for
    example - within urban areas.
  • IPCC UHI does not exceed about 0.05C over the
    period 1900 to 1990, because
  • land, sea, and borehole records are in agreement
  • the trends in urban stations for 1951 to 1989
    (0.10C/decade) are not greatly more than those
    for all land stations (0.09C/decade).
  • the differences in trend between rural and all
    stations are also virtually unaffected by
    elimination of areas of largest temperature
    change, like Siberia, because such areas are well
    represented in both sets of stations.

12
Urban Heat Island (2)
  • Peterson, J Clim, 2003 "Assessment of urban
    versus rural in situ surface temperatures in the
    contiguous United States No difference found"
    indicates that the effects of the UHI may have
    been overstated, finding that Contrary to
    generally accepted wisdom, no statistically
    significant impact of urbanization could be found
    in annual temperatures. This was done by using
    satellite-based night-light detection of urban
    areas, and more thorough homogenisation of the
    time series (with corrections, for example, for
    the tendency of surrounding rural stations to be
    slightly higher, and thus cooler, than urban
    areas).
  • Parker, Nature 2004 attempts to test the urban
    heat island theory, by comparing tempature
    readings taken on calm nights with those taken on
    windy nights. If the urban heat island theory is
    correct then instruments should have recorded a
    bigger temperature rise for calm nights than for
    windy ones, because wind blows excess heat away
    from cities and away from the measuring
    instruments. There was no difference between the
    calm and windy nights, and the author says we
    show that, globally, temperatures over land have
    risen as much on windy nights as on calm nights,
    indicating that the observed overall warming is
    not a consequence of urban development.
  • Publication bias Peterson notes that essentially
    all large-scale studies showed some urban centres
    cooling. But no individual city studies did.
    People were reporting what they expected to see.

http//www.ncdc.noaa.gov/oa/rural.urban.ppt
http//en.wikipedia.org/wiki/Urban_heat_island
13
Hockey Stick controversy...or,The temperature
over the last 1-2 kyr
http//en.wikipedia.org/wiki/Image1000_Year_Tempe
rature_Comparison.png
14
The day after tomorrow...will not happen
  • Simulations using the HadCM3 climate model of the
    Atlantic thermohaline circulation from 1860-2000
    (using historical variations of greenhouse gases,
    sulphate aerosol, solar radiation and volcanic
    dust). The simulations show a freshening of the
    Labrador Sea from 1950-2000, as has been seen in
    observations, but this is associated with a
    slight strengthening of the thermohaline
    circulation over the same period, rather than a
    weakening as has sometimes been suggested. When
    the simulations are extended forward from
    2000-2080 (using a projection of future
    greenhouse gases and aerosols), both trends are
    reversed, with a salting in the Labrador Sea and
    a weakening thermohaline circulation

http//www.metoffice.com/corporate/scitech0304/cli
mate_surprises.html
15
Ozone hole/depletion and climate change
  • Although they are often interlinked in the
    popular press, the connection between global
    warming and ozone depletion is not strong.
  • Global warming from CO2 radiative forcing is
    expected (perhaps somewhat surprisingly) to cool
    the stratosphere. This, in turn, would lead to a
    relative increase in ozone depletion and the
    frequency of ozone holes.
  • Conversely, ozone depletion represents a
    radiative forcing of the climate system. O3
    losses over the past two decades have tended to
    cool the surface.
  • One of the strongest predictions of the GW theory
    is that the stratosphere should cool. However,
    although this is observed, it is difficult to use
    it for attribution (for example, warming induced
    by increased solar radiation would not have this
    upper cooling effect) because similar cooling is
    caused by ozone depletion.

16
CO2 emissions... reductions?
  • Of the "frontrunners" one is an order of
    magnitude bigger than the rest Extend UK
    participation in EU carbon trading scheme (4.2).
    Means don't actually produce less CO2, but buy
    permits to emit it.
  • Of the "emerging" category, the two biggest are
    Introduce ways to store carbon pollution
    underground (0.5-2.5) (i.e., don't produce any
    less, just...) and Force energy suppliers to use
    more offshore wind turbines (Up to 1). Which
    would actually save CO2.
  • In the "difficult" category the biggest is Change
    (read enforce) road speed limits (1.7) - a
    surprisingly large number.

17
Evaluating Impacts
  • Not really my thing just some ideas
  • Of the Consensus View, the weakest point is
    ...and it will be a bad thing. Which is not to
    say its wrong, just harder to evaluate. Risk
    change from what we (and ecologies) are adapted
    to.
  • Sea Level Rise is fairly obviously bad, but
    probably slow (surprises?)
  • Ecological impacts I don't know but difficult
    political choices how many flights to go skiing
    are people prepared to forgo, in order to save
    polar bears (were that the choice).
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