Title: Climate Change
1Climate 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
8Common 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...)
9Satellite 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)
11Urban 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.
12Urban 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
13Hockey Stick controversy...or,The temperature
over the last 1-2 kyr
http//en.wikipedia.org/wiki/Image1000_Year_Tempe
rature_Comparison.png
14The 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
15Ozone 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.
16CO2 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.
17Evaluating 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).