scientists tell us that the world is
warming and other there's much
uncertainty regarding the extent of the
warming at its consequences there is
broad agreement that a warmer climate
will affect whether sea levels
ecosystems and agriculture clearly is a
lot of uncertainty about the future and
I suppose the uncertainties come from
different things uncertain what the
future concentrations a greenhouse gases
will be and then it's uncertain how the
earth if you like as a system will
respond to that warming how do we make
decisions about our environment when
there's so much uncertainty climate
change science offers us no simple
answers however using statistics we can
build upon our assumptions using
rational methodologies to arrive at
meaningful recommendations climate
change has been happening for eons so I
think the question that society probably
cares about is whether climate change
caused by emitting greenhouse gases is
real there's been a lot of research in
the last two decades that's really been
able to say pretty definitively that
humans are contributing to the climate
change that we're experiencing today
marketers is one of many scientists
documenting changes in our planet's
climate and its effect on ecosystems
climate change is not a new phenomenon
but what is new is the rate at which
it's changing you know you think of the
difference between a slowly rising tide
and a tsunami right and that's sort of
the difference between maybe climate
change under natural historical
conditions and climate change that we're
projecting over the coming decades and
centuries climate change is most visible
where water meets ice this is where a
small change in temperature has the
biggest effect we see a lot of evidence
of climate change in these cold
environments and we've seen it early
there and we've seen it very strongly
there nowhere is this effect more
visible than in retreat inglesias
retreating and shrinking glaciers are
the single most tangible evidence of
climate change in the world today and
that's what our cameras are capturing we
have cameras in Alaska in the Rockies in
Greenland and Iceland we've been
watching glaciers in the Alps and in
Bolivia and so we're seeing the same
story everywhere ninety-five percent of
the glaciers in the world outside
Antarctica are retreating and thinning
and shrinking
there's also strong evidence that has
ice melts and temperature rises sea
levels are rising what we find here in
this dock in this area is that sea
levels have been rising at one point two
millimeters per year since the 1930s in
fact the last two decades they've been
rising rather more rapidly than that but
we do see a definite rising trend in sea
level here in Southampton and we see
rising sea levels around most of the UK
and the explanation for that is that the
ocean volume is growing and the way to
explain that is that the oceans are
expanding as they warm and also that
land-based ice is melting and flowing
into the sea and increasing the volume
of the ocean how much will the sea level
rise the estimates vary but it could be
as little as half a meter but it could
be that if the whole of the polar ice
cap melts the water could be lapping
around on the road of the Golden Gate
Bridge
but studying the visible effects of
climate change are only part of the
story many scientists are trying to
understand how a changing climate will
affect the complex interactions among
plants and animals within ecosystems at
nearly 3500 meters above sea level pine
forest gives way to a community of
plants that makes up alpine tundra what
we're really interested in is how the
overall landscape is going to change and
with warming temperatures we think that
they may be forced to move upward and
elevation but we're at the top of the
mountain nearly a number of people have
developed computer models that predict
that a lot of these species that are
growing at these high elevations may be
very challenged to to make it
essentially as the climate warms and and
their habitat might be pushed sort of up
and off the tops of the mountains and so
we're experimentally essentially testing
some of those models that people have
developed Larry Cooper's researchers are
heating small plots of seedlings through
the winter and summer to document the
effect of future temperature changes on
pine tree germination and growth so the
infrared heaters here are causing the
snow to melt earlier there are plots
right nearby around this one that don't
have infrared heater arrays and they're
still covered in snow if they had the
heater raised they'd also be melted out
but because they don't they're still
covered basically we've sown these seeds
into these garden plots and some of the
plots were experimentally warming with
these overhead heater arrays and others
were just leaving to be what we call
control plots to get out the key
question of whether climate change is
going to going to affect the ability of
tree species to get established in the
tree line
but there are some really healthy
seedlings in here that have survived
over the winter they germinated last
year and so it's not surprising you know
that if you sow a seed the plant will
grow the question is how are the
probabilities changing across the sites
and with the with a warming climate one
of the problems for scientists try to
understand the effects of climate change
is that this change occurs over long
periods of time and few have the luxury
of studying change over a lifetime one
scientist who recently found himself in
the center of climate change debate is
James Thompson for 20 years he's been
studying a small perennial but blooms at
high altitudes high elevations pose some
special problems this is where we might
first see things like species doing
poorly because the situations have
changed essentially I've asked a very
simple question what causes a flower to
be a success does it get pollinated does
it set a fruit does it make seeds how
many seeds does it make what he's
discovered is that as the climate warms
the snow melts earlier causing the
glacial lily to bloom earlier basically
these require a visit from a pollinating
animal to succeed but there is
unfortunately a deterioration in the
pollination service they're getting the
flowering is tending to happen earlier
in the spring because the snow is
melting faster than it used to and I
think this is some manifestation of a
climate change effect this is a plant
that might be subject to getting
dislocated in time from its pollinators
and in fact that seems to be happening
scientists not James Thompson the
finding that the effects of climate
change are both subtle and profound
affecting many species and ecosystems in
ways that as yet we do not understand if
climates are changing relationships
between plants and pollinators and other
new
beneficial relationships those may be
disrupting these glacier lilies are a
cog in a pretty complicated ecosystem
and maybe not a trivial one we don't
know how many species and how many
ecosystems are affected and we're
uncertain about the consequences of
these effects little differences in how
individual species respond to climate
change tell us something about how the
whole biosphere is going to respond to
climate change and so species here and
there ultimately sort of come together
to tell a fuller story while this fuller
story continues to unfold there remains
much uncertainty for policymakers who
face two approaches to climate change in
principle we could try either to prevent
global warming or we could try to adapt
to it we're going to have to be doing
some a tribal court adaptation to to the
effects of climate inevitable climate
change and there but then I think
mitigation is important to limit that
change to what we can manage think we
need to do both you know we need we need
to try and reduce global warming by
reducing less greenhouse gases but we'll
need to adapt to the changes that result
from those we have a mission preventing
climate change or mitigation requires
new technologies and global action to
reduce gas emissions both of which are
uncertain so in this film we ask how can
we make sensible decisions about
adaptation to climate change the sea
level is rising weather patterns
changing agricultural zones are shifting
how can we make sensible decisions about
where to focus our limited resources to
best adapt to climate change one way of
looking at these problems is to apply
monetary values to the costs and
benefits of adaptation and then use
statistical methods to make sensible
decisions about where to focus our
limited resources
but before we can do that we need to
consider a concept that we call
discounting people prefer the current to
the future we know this because you have
to pay an interest rate if interest
rates of 5% people are saying I'm
indifferent between a hundred pounds
worth of benefits now and a hundred and
five pounds worth of benefits in a
year's time the future is worth less to
us than the present we can work out the
discounted value of some some the
present value pv for any interest rate
for any future time period and we use
the formula but pv present value equals
a over 1 plus R to the power n where a
is the sum of money we're talking about
r is the appropriate interest rate and n
is the number of years into the future
that we're considering suppose we had a
ten percent discount rate we're saying
that we're indifferent between a hundred
pounds now or 110 pounds in a year's
time or to put that another way we'd be
indifferent between 82.6 pounds now and
a hundred pounds in two years time
because if we had 82.6 pounds now we
could invest it at a compound interest
rate of ten percent and turn it into a
hundred pounds in two years time
our table shows us the present value of
one pound at various interest rates in
200 years time we're looking at a period
well into the future because global
warming policies will continue to have
an effect for a very long time given a
discount rate of five percent the
present value of one pound received in
200 years time is only naught point zero
zero zero zero five eight pounds on this
basis we might argue that you'd have to
love your grandchildren a great deal if
you're willing to give up at say a five
percent discount rate 10,000 pounds now
so that they could have 58 pence in 200
years time discounting is a
well-established idea there's useful in
making investment decisions for instance
using discounting to make decisions on
motorways or high-speed rail lines makes
sense but does it make sense when
considering adaptations to climate
change some think so but not all would
agree that it does well public policy is
all about values and it's essentially
saying that as people who live now we
care more about the wealth that we're
going to accumulate there are other
problems with discounting you might feel
the climate change raises ethical issues
because costs are not born within an
investment silikal but by future
generations you might be concerned that
costs of adaptation are not born evenly
by also some at ease for instance
European nations are already preparing
for sea level rise and will suffer
relatively minor effects whereas some
nations may be completely inundated sea
level rise in Europe is an engineering
challenge but for other parts of the
world it may obliterate nations and
cultures similarly damage the habitats
in mountains and coastal regions will
cause extinction of many species
any value we assigned to this will have
large uncertainties attached to it there
are further problems when we think about
the distributional effects suppose
there's some policy which is going to
lose one dollar per day per person it's
pretty trivial unless you're a
developing world farmer in which case it
might mean the difference between life
and death will return to the question of
the distribution of income in a later
film there are no right answers here
because we're not always agreed about
the costs and the benefits involved but
what we are interested in is the
methodology so let's look at some
estimates that have been made but not
get too hung up on the numbers let's
just understand the methodology given
was so unsure about the risk factors
will proceed here on the basis that
we're dealing with uncertainty so how do
we make a rational choice when we're so
uncertain about the future there are
four possible decision rules and the
first one we use is the principle of
insufficient reason that says we have no
sufficient reason for thinking that one
outcome is any more or less likely than
any other so we'll attach an equal
probability to each of the outcomes in
our case we have three possible outcomes
so we'll attach a risk factor of one
third to each possible outcome to
illustrate the approach will simplify
and have just three possible scenarios
the first we've labeled optimistic where
we assume that the effects of global
warming will be relatively small and
benign pessimistic where we assumed that
the effects of global warming will be
relatively large and damaging and medium
where we assume something between the
other two possible outcomes
we have three policy possibilities as
well strong where significant policies
are taken to modify presumed global
warming damage week where little is done
and moderate where some policies have a
fairly limited nature are undertaken the
values in the table show the annual
percentage loss of world income gross
domestic income associated with each
outcome don't be fooled by the
apparently trivial numbers world income
amounts to many trillions of dollars so
each percentage point represents a
severe loss of well-being
notice that on an optimistic scenario it
would have been better to have a weak
policy or maybe do nothing this is
because the damage would have been small
anyway and we've wasted scarce resources
dealing with it unnecessarily so how do
we make a rational choice of policy when
we don't know for sure the seriousness
of the damage of global warming we're
looking for possible strategies for
making a choice under uncertainty the
first strategy is to use the principle
of insufficient reason this principle is
that we have no sufficient reason for
thinking one outcome to be any more
likely than any other and on this basis
we attach an equal probability to each
outcome in our case it will be one-third
and proceed as if we were in a situation
of risk with these known possibilities
so the expected value EV of a strong
policy is EV will be 4.5 times a third +
3.5 times one-third plus 2.5 times a
third which equals 3.5 so with a strong
policy the expected value is
three-point-five percent of loss of GDI
annually then with a moderate policy the
expected value will be 2.5 times the
third plus 3 point 8 i'ma 3rd + 3.5
times a third which equals 3.0 and with
a weak policy EV comes to 2 point 0
times the third plus 3 point 8 i'ma
third plus 7 point 0 times the third
which equals 4 so given that we're
trying to minimize the damage a moderate
policy is optimal taking some steps but
accepting that the cost of some steps is
greater than the expected benefits of
course if the risk factors are known we
could work out an EV using those values
so if it's agreed by the scientists that
the pessimistic forecasts is much more
likely we could rework using these
weights to get a new EV
and possibility is suitable for the
optimist this is sometimes called a maxi
max policy assume that the best will
always turn up so looking at our table
again here we presume that if we pick
strong as our policy then we'll lose the
least income only 2.5 for moderate will
also lose 2.5 because we assume an
optimistic outcome and for weak 2.0 so
given our optimistic assumptions
minimizing the loss requires us to
choose a week policy option will choose
that and optimistically hope that we
only lose two percent of GD I per annum
a third possible strategy is suitable
for the pessimist assuming that the
worst will always turn up so looking at
our table again here we assume that if
we pick strong then we may lose 4.5 that
would be the worst possible loss of
income for moderate we might lose 3.5
and for week as much as seven percent so
minimizing the loss requires us to
choose in this case a moderate policy
option because the worst we can then
lose is 3.5 percent of annual GDI
so that's our maximum strategy as it's
called
this one more
to consider with an issue like climate
change if we get it wrong it could be
extremely serious so we may want a
particularly cautious approach then we
might want to use the minimax regret
approach the essence of this approach is
to look at the extent to which we might
regret any particular choice we've made
and then pick the option which minimizes
the regret that will have you're turning
to our table we first construct a regret
matrix for each policy we ask once the
maximum regret that we could have if we
pick a strong option and the optimistic
forecast is correct we lose four point
five percent of GD I when by picking
week we could have lost only two percent
the regret we have is their poor 2.5%
the difference between what we got and
what we could have had if average turns
up we regret picking strong but only by
one half of one percent of GD I if
pessimistic turns up there'll be no
regret at all I can perform that same
operation for moderate and weak policies
and then that gives us our regret matrix
our policy strategy is now to minimize
the maximum regret if we choose strong
our greatest regret would be that it's
cost us two point five percent of GD I
for moderate one percent and for week
four point five percent so minimizing
the maximum regret requires us to choose
in this case and under these assumptions
a moderate policy
of course the policy recommendations
we've come up with depend upon the
uncertain assumptions that we've made
there isn't a right answer that we found
but if we understand the statistics we
have an approach an approach which is
suitable for examining problems either
in the public or the private sector when
there are issues of uncertainty involved
scientists continue to refine climate
change models the evidence for global
changes continues to mount and
scientists are beginning to document not
just the global effects but the small
local changes that enhance our
understanding of locally effects and
consequences as our knowledge improves
the uncertainty may well diminish and it
will be possible to make more precise
policy recommendations using statistical
methods like these we've examined and
there's always the possibility that we
might seem really very large changes and
I think it is sort of risk management
sense those large changes are worth
avoiding and the worlds of stress system
already I think like it's not just
climate change impacting a world without
other problems it could be the straw
that breaks the camel's back I'm
regularly surprised by how sensitive the
Earth system the biosphere is to what we
might think of as pretty small changes
in the climate I see these as important
challenges that if we if we ignore them
and put our head in the sand then we're
going to live in a pretty frightening
world but as long as we keep our eye on
these issues and we don't ignore them
then I think society should be able to
to adjust and deal with them but that's
the sooner we can act that the easier it
will be to do something
we think we know a lot about the natural
environment but every year there's a new
surprise and I don't know what it'll be
this I don't know what it'll be this
year but I'm sure that there will be one