Good evening everyone

I have to confess, that after a pretty gruelling meeting last week

I'm feeling a little bit tired

so I hope I can do justice to the fact that

so many of you have turned out here.

It's absolutely marvelous to see this level of interest

in what for me is 30 years of work

and you think of it differently because you work inside the field for so long.

But now we're realising how important it is for the future of the planet,

for the future of the human race.

And that applies even to scientists like me

who have been working with the stuff for 30 years

we are still coming to a realisation,

I think because of the enormity of the issues

and the depth to which we are going to have to plumb our ability

to change the way we operate on the planet.

So let me not rave on too much. I'm going to cover the physical sciences

I'm going to tell you about how we pulled our report together

Well why don't I show you this slide:

I'm going to tell you about the changes we are seeing happening,

what we know from physical principles is it changes climate

and a particularly important issue for the community I represent is:

can we really say that people are doing it?

I really want to stress that, because in a sense, the science community

is now telling society that it is going to have to change

You don't do that lightly, this involves huge amounts of re-organisation

so it is something we take very seriously.

And now I will tell you a little about what we can project for the future

and how we go about doing that.

So the report of Working Group I

There are four reports mentioned already tonight to come out from the

IPCC this year, the Working Group I Report came out in the

very beginning of February, by the time we got the final approval.

The front cover looks like this - this is the one on the physical sciences

where most of my material is coming from

We started a scoping process involving international research

organisations figuring out where the new developments

were in the science back in 2003

We had 152 authors, I guess that has already been mentioned

We also had about 450 people who also sent in revised figures

and other bits and pieces of information

We take a review process very very seriously in the IPCC process.

We create two drafts, a first and a second draft.

Each of those goes out for review.

The first is called an Expert Review and the second is a Parallel Expert and Government Review.

Anyone can call themselves an expert - anyone can review this stuff -

it is all out there on the web and you can get hold of it.

Too late now of course as it is all over now.

We got more than 30,000 comments for those two reviews

Every one of those comments has a written response

from the author team and all that is a matter of public record.

This is a very open and transparent process.

This is not just like writing another science paper and seeing whether

you can get it published somewhere.

This is a very thorough process.

You can see the table of contents there.

I will mention one other statistic on that slide -

which is there are about 5000 scientific papers,

literature references that are assessed in this report.

Most of those have been published within the last six years

There is a huge amount of research activity out there underpinning

what we are doing and the assessment process is not to do research

it is really to provide a snapshot of our understanding

for the policy community, and for ourselves frankly,

it is based very much on what is in the literature

If it is not on the literature then it gets weeded out.

One of my jobs for example, in exercising quality control on this report,

was to figure out where some author had a paper in the back of his

head, that he was going to publish after he got finished with

his chapter for the report, and say "No, no, no, you can't cite that

because it is not actually out there, and I cannot show it to a

reviewer to say where your information is coming from."

It has got to be a real paper - got to be on the literature.

So all this is available on the web, that's the URL. You can get all our

figures in PowerPoint format if you want to use them, and as I have

already said all the review, comments and responses are publicly

available there, warts and all.

Some people will go through that and say the authors didn't deal with

something well enough. That's okay - maybe we didn't -

but at least you know what we did.

Let's talk about what's happening.

The primary index of what is happening to the climate of the planet

is the global average surface temperature.

The way we track it actually, is to look at changes

averaged over the planet

Obviously the temperature in Jakarta is very different to the

temperature in Dublin, most of the year at least.

So what you do is you're actually tracking the variations.

You have a climatic norm, a climatic average which takes into account

the geographical variations, and takes into account

the seasonal variations from winter to summer.

So we are looking at departures from that.

Each of these dots represents a temperature anomaly,

calculated that way for a particular year.

The blue band shows you a smooth version of that wobbling around

we had a bit of a warming in the 1940's, around 1940,

and then it flattened out a bit, and then it went up again.

If you put a straight line through this simple mathematical exercise

you get a slope of about .05 degrees per decade, going up a bit.

That was over 150 years.

If you fit the line to the last hundred years, the slope picks up a bit.

If you fit the line to the last 50 years, it goes up to about .12

or .13 degrees per decade, and for the last 25 years

we've been running at about .17 or .18 degrees per decade.

So when we put this figure together and it went out to review

our authors came under some pressure to say "oh so warming is

accelerating". We deliberately did not use the word 'accelerating',

because as I will show you later on, the projections for the near term

future are to continue at about this rate of about .2 degrees per decade.

I think we need to turn that around because what it says to us

is that climate change started about 25 years ago.

If you think climate change is out there and it is something that is

going to happen, then it is later than you think.

We've been living with climate change now for about 30 years.

That's why the people who studied the impact and the effects of

climate change, can actually see real results and so in the

Working Group II report, that I am not going to talk about,

they have a lot of material that they can show

how we are seeing real change.

We are living with change now and we have been doing so for 25 years or more.

This warming pattern is not totally uniform but

the warming trends are pretty well everywhere

This is a map showing darker reds where there's a higher trend,

a higher warming rate, and it goes back to 1979.

I should have put that on the slide.

But the reason that we picked 1979 is that it's the start of the satellite records.

It is a reasonable statistic to look at.

You will see there are some light blues here. There are some places on

the planet that are actually cooling, and that may go on for a while,

but we expect that to turn around.

And you see there are places that are warming

quite a lot more than others.

The land is warming more than the ocean.

Some people ask the question well is that simply because we've got so

much industry and we've got all these cars driving around, aeroplanes

and things shooting around and so they are obviously generating heat.

Houses generate heat, industry generates heat.

Is it just a local effect?

Well one way you can test that, is you can look at this other map

that was generated some time ago showing the lights at night across

the planet. I apologise the two map projections are slightly different,

I hope by eye you can line things up.

You see there for example, the United States where I have been living,

most of the lights are on the eastern side of the country.

Most of the warming is on the western side of the country.

Look at northern Canada most of the warming there is in the high Arctic

where people don't go very much unless you are an Inuit.

Look at the warming in Greenland.

The warming in Europe is not clustered around the industrial centres.

Look at it in China, in Africa, the patterns are different.

If this was all just coming from local energy, you would expect a good

match between these patterns - you don't.

There are many other reasons, I am just giving you one, why

we know what we are seeing is actually a planetary scale phenomenon

and it is not some local effect.

I will come back to that a little later.

So a lot of other things are changing as well and I don't have time

tonight to go through all the things about how rainfall patterns are

changing etcetera, etcetera.

I will give you a list in a little while but I do want to make the point

that our report came out in February and within months we had

basically seen further dramatic change in the planet.

This isn't stopping, it just keeps on going,

and science is struggling to keep up.

I'll say more about that later on.

We said in our report, the text there in white on the upper right,

that the Arctic Sea ice extent is decreasing by 2.7% per decade since

1978 based on satellite measurement,

with larger decreases in the summer.

On the curve on the lower right you see there is an upper grey line,

I hope you can see, which is the average cycle during the summer

of the area of ice in the Arctic. You see it hits a low point

in early September.

The dotted line underneath it was the previous record low in 2005

well below the average.

The blue line which doesn't complete - is this year.

We dropped 20% below the previous average which was in 2005.

We are just seeing things happen that we don't actually expect always.

Our climate models have to track what's going on

with the ice in the Arctic

Because ice is very important, in that it reflects sunlight, very white -

And what that means, is that all the light energy coming in

bounces straight back out and doesn't really warm the planet.

So the ice, not only is it cold, it actually acts to cool the planet.

Once the ice melts, as this little feedback loop I am showing indicates,

you get a very dark coloured ocean, that mops up all the incoming

energy and that then goes into warming the water.

Warmer water melts more ice and so you get the feedback loop.

A little bit of ice goes - warmer water - more ice melts etc.

Those things are quite hard for us to get right in some of our models,

but the models have to practice stuff, as I said a minute ago,

and the 2007 number - the Arctic Sea Ice extent - is lower than

any of our projections, including the ones we were making a year ago.

The planet is moving quickly.

I am going to talk about sea level from a couple of different perspectives

but I just want to show you a long term record.

The record of sea level come from different sources and you can't

always combine them very easily.

The red dots are one set of measurements

from tide gauges around the world.

A lot of harbours and things like that tend to track tides. Obviously tides

go in and out and change sea level by quite a lot, but you get the

average for the year, and then you do it for many years, and start to

see a trend - coming up like this.

And the blue dots are another compilation of more tide gauge data.

The little black line, right at the upper right is new data from satellite.

Satellites can actually pick up the fact that sea level is rising.

The reason this is linked to global warming, is because we know

most of rise occurring now is because the ocean is getting warmer.

When you warm water it expands and if it is in the ocean it's only got

one way to go - when it expands it has to go upwards.

The sort of reason why we know this is happening

is shown here in these two maps.

The upper map is showing the sea level rise pattern, with red meaning

it is going up by so many millimetres per year.

You can see a little colour bar there in the bottom

Some places it is going down sea level actually is influenced very much

by things like El Niño events.

This is only over ten years, this is not a long term record,

this is just a snapshot.

Over ten years we saw some places go up and some go down.

The important thing here is the figure at the bottom shows you the

change in the heat content of the ocean and there is a pretty good

match between those two things.

That's the sort of evidence we have for knowing that the sea level rise

we are seeing is largely driven by ocean warming.

Independently of all this we have records of the ocean temperatures

now going back more than 50 years (good measurements),

some measurements go way back but they are not very comprehensive.

We can say the oceans categorically have warmed

to depths of more than three kilometres in all ocean basins.

The oceans are getting warmer just like everything else is

hence sea level rise.

There is a consistent pattern here, we are getting surface temperatures

increasing. The troposphere i.e. the atmosphere above us up to 10km

the temperatures are increasing all the way through there.

Atmospheric water vapour is increasing, which is linked to increasing

precipitation, particularly heavy precipitation events,

I have just said the ocean heat content is increasing,

which is linked to sea level rise,

Greenland and Antarctic ice sheets are losing mass,

glaciers and snow cover decline.

We have talked about Arctic sea ice.

Permafrost or seasonally frozen ground is decreasing.

melting, a lot of thaw going on in the high arboreal region.

Wind patterns are shifting we are seeing storm tracks moving,

we are seeing more intense and longer droughts,

we are seeing more frequent heavy precipitation events,

we are seeing extreme temperatures, increasing tropical cyclone intensity.

There are physical linkages between all of these things and that is why

our author team choose the word 'unequivocal'

to talk about what we are seeing.

Climate change is here. It is unequivocal. It is happening.

I am not using that word for the human attribution argument,

I am using that word very carefully

for the observations we know about the change.

If you want to look further back in time, this is a number of different

temperature records, inferred in different ways, stretching back to 700AD.

The bottom axis shows you the calendar year running up to 2000.

The vertical axis is the temperature anomaly curve again.

These sorts of measurements come from things like tree rings, corals,

from lake sediments, where there are

temperature sensitive changes going on.

What people who study these things do is they look to something

where they know there is an environmental indicator that is

sensitive to its local temperature or its regional temperature and

then they look for records of that, either in sediment cores or in ice or

wherever you go - coral.

Many of them actually only tell you what is happening in the summertime,

because if it is a tree ring it maybe more sensitive to the growth period

rather than the dormant period in winter.

Some of them are seasonally specific - some of them are regionally

specific but you get a pattern emerging.

We are saying this is our best estimate to what has happened to the

Northern Hemisphere temperature because though between them those

different records cover virtually all of the Northern Hemisphere

fairly comprehensively.

The black record, the black line right on the end is the instrumental

record, we have enough thermometers at Met stations

all around the world to start to put those records together,

and those are the ones I showed you earlier.

You can see that there was something like a warm period around

about 1000AD sometimes referred to as the Medieval warm period

You can see there is a cooler period after that around the seventeenth

and eighteenth centuries perhaps.

Changing by about a half a degree perhaps.

Now a thousand years ago people were growing potatoes in Greenland,

and in the seventeenth century there were ice fairs on the Thames,

because the ice froze so solid that it was used for a playground.

Half a degree change in global mean.

The big difference between the global mean temperature which doesn't

have to change very much to actually start to make

significant regional differences.

These changes we know historically have been quite important and

the changes I am going to show you for the future are

significantly larger.

Time to talk about things driving climate change and perhaps time for

some historical relief.

I am showing you here a picture, painted I don't know when, I guess

probably in the seventeenth or eighteenth century depicting the Greek

myth of Daedalus and Icarus. I know I am in a city of enormous literary

background but I will remind you of the story anyway.

Daedalus was an inventor who was put in a maze by the king of Minos

and he had to try and escape somehow, so he decided he was going

to build wings with feathers of birds, that he could actually get together

he used wax with the feathers to make some wings

and his son was with him, and so he made wings for both of them.

They managed to fly out of this maze they were trapped in.

The son, Icarus being young and impetuous - and I relate to this very well

because I have a young and impetuous son - well younger anyway

flew too high in the Greek myth, and the wax in the wings melted,

the feathers fell away, and he fell to his death.

That's a Greek story, but of course there is something terribly wrong

with it isn't there?

Because as you go up it gets colder, so you see the Greeks actually

knew quite a lot about Geo-science, they had actually calculated

the radius of the earth, and they weren't that far out.

They knew the sun heated the planet, but they didn't know something

called the Greenhouse Effect. What is the Greenhouse Effect?

Well the planet is warmed by the sun

but ironically the air is warmed by the earth.

The energy comes in and it comes straight through. It is not really

absorbed by the air, it is coming in, really, as visible light.

When it hits the Earth it warms up the Earth and it goes back out as

infra-red radiation, something like the radiation you get off an infra-red

heater, and that radiation coming back out is absorbed

by certain molecules in air, and these are the Greenhouse gases.

The air is heated from below.

The presence of these Greenhouse gases in the atmosphere raises the

surface temperature by about 30 degrees, because as the air warms,

it then re-radiates everything, and so it warms the surface up again.

Increasing Greenhouse gases we know increases surface temperature.

This has been known since the nineteenth century

and there is a grand old guy, I'm showing his photo here,

Svante Arrhenius, who was a Nobel prize-winner.

He won a Nobel prize for Chemistry.

The thing he is most remembered for now actually,

is he did the first calculation of what would happen,

if we doubled the amount of carbon dioxide in the atmosphere.

He knew carbon dioxide was a Greenhouse gas. He knew it was doing

the things I have just described, and without the aid of computers,

basically with pencil and paper, he sat down and worked this out.

It must have taken him quite a long time.

He made a few mistakes, but he came up with this number of 4°C,

which would occur if we doubled the amount of CO² in the atmosphere.

He also said that -the second sentence is a direct quote from his book -

the percentage of carbonic acid which is what they called CO²

made by the advances of industries be changed to a noticeable degree in

the course of centuries and in that he was wrong.

Geochemists at the time thought that if you put CO² into the atmosphere

there is no problem, the ocean will just mop it up because it is a

soluble gas, it is a weakly soluble gas, but it is a soluble gas,

so it would just dissolve into the ocean no worries.

Well a guy called Roger Ravel, who was a marine chemist,

came along in 1950 and suddenly figured out that was all wrong,

and that there are things called buffering reactions in the chemistry,

and the ability of the ocean to mop up extra CO²

was very much less than previously people had thought.

Then he got a student of his, Dave Keeling,

to start measuring CO² in the atmosphere

and from about 1958 onwards,

we've known that CO² is going up much faster than Arrhenius thought.

Now we come on nearly 100 years later, and probably spending several

hundreds of millions of dollars of research money, your taxes perhaps,

the IPCC holds all the science papers

and comes up with a statement that if we double CO²,

the warming is going to be about 3°C of a likely range of 2°C to 4.5°C.

It is not a million miles away, and it is a real tribute to Arrhenius,

that he was able to get so close when he didn't have any super computers.

Now we know that "business as usual" as we would call it scenarios

for emitting carbon dioxide will lead to a doubling this century.

I'll come back to that again.

There are a lot of other things that can potentially drive climate and

I should mention that we acknowledge for example that changes

in the energy coming out of the sun obviously is one of them, changes in

the Earth's orbit around the sun, has obviously been very influential

in the geological past, and we believe has been the main trigger

for the formation of Ice Ages and then the intervening warm period.

But here are the agents that we think are most active right now

They are displayed here on a bar graph and the units you can see down

the bottom are what we call Radiative Forcing (Watts per metre²).

It's the perturbation of the energy balance in the atmosphere

that these gases are causing now, relative to

the energy balance that existed in pre-industrial times - 1750.

Carbon dioxide is out there as adding one and a half watts per m².

Think of what a family house and garden occupies these days.

It's a couple of kilowatts or something of that order over the

area of your property, but it is over the whole planet.

It's a significant amount of heat.

We have got some other Greenhouse gases in here the second bar

is mentioning methane, Nitrous oxide and halocarbons, a bunch of things,

including gases incidentally that are ozone-depleting substances and

are already controlled under the Montreal Protocol, an ironic thing,

the Montreal Protocol has done more to reduce climate change than

anything else we have done.

The stratospheric ozone is getting lost and that is leading to cooling

as ozone is a greenhouse gas, tropospheric ozone is increasing,

you can go on down the list.

Land use change, we think has probably had a net cooling effect.

Then there are these things called aerosols, small particles that come

mainly because we are emitting sulphate species into the atmosphere,

associated with burning coal and oil.

They form small particles that reflect sunlight coming in, so they have

a cooling effect just like I said - ice bounces light straight back into

space, these small particles are doing that to some extent as well.

They also change cloud properties, and make the clouds more

reflective, so they are having a definite cooling effect.

We can now calculate the net effect of all these activities down

the bottom, it is about the same as carbon dioxide.

The rest of the other warming and cooling more or less balances out.

There are some fish hooks in that, which I might get to later.

Carbon dioxide, its perturbation of the energy balance in the atmosphere

is increased by 20% just in a decade. This gas is going up.

It's making a big difference.

I want to give you a feel for what a Watt/m² is

This total which we are currently disturbing the energy balance by

If you add up all the power stations on the planet, all the nuclear

power stations, all the hydro, all the energy that comes from oil

and gas and everything we put in our cars,

all the primary energy production,

it is one fiftieth of the energy that we are putting into

distorting this environmental balance in the climate system.

That's another reason, of course, why we can't accept that the

temperature changes are due to the industry, and the energies

and planes and motor vehicles.

We know, and this is all basic physics, we know that the distortion of

the radiative balance in the atmosphere is fifty times larger than that,

so that is what is driving the temperature changes.

Now we have the ability to follow with climate models something

about how these things play out over time.

I want to show this graph which goes back to the temperatures

over the last thousand years, which are shown there in grey shading.

and show, first of all, how our understanding of climate tracks that

reasonably well - it doesn't track it perfectly - frankly we would like

to A) know the temperatures back there better than we really do

we would like to know some of the other drivers, which are

in this case, solar change which we are inferring

in these sorts of studies from sun spot data and volcanic eruptions,

because volcanoes tend to cool the planet, but only in a transient way,

and they give us a cooling spike.

So you can see we are warmer here, and cooler here, remember I

talked about the half a degree difference between the Medieval

warm period and the little ice age

The climate model is tracking that largely due to solar changes.

Then we are getting all these negative spikes. These are largely due

to big volcanic eruptions, including here in the nineteenth century.

Around here, when the book Frankenstein was written by Mary Shelley.

because it was a year with no winter, and they were all so depressed

they all had a competition to write some horror story, and she won.

At the end of this record the very right end, you can see these thin

lines here, this is what the temperatures would do if we didn't add

greenhouse gas increases to our model, and the thick lines are

what happens if we do.

I want to now look at this whole last century in more detail.

I am going to take decadely average temperatures.

Something I need to point out about climate models - climate

models don't predict this year's weather and next year's weather.

They really are averages, and so where they are most reliable

is when we are talking about averaging over a decade and

averaging over a large region.

So this is now showing the temperature data decade by decade.

If we use models that don't have greenhouse gases in

this is the best they do.

This tracks the solar changes that we've observed, the solar changes

that are our best estimates of how energy coming

out of the sun has changed.

It's tracking a little bit of volcanic activity in that period and if we

add in the greenhouse gases we get the pink curve instead of the

blue one and it is a pretty good match.

And, we can do this, we can break this down region by region.

I mentioned that land is warming faster than the ocean.

If you look carefully at the global versus the global land plot here,

you will see the observed line, the dark black line is much sharper

in the last 30 years for global land than it is

for the total of land plus ocean.

You might have noticed earlier that there is this period in the 1940's

when we got a warming, and the models don't track that.

I guess we didn't have enough measurements in place to know

exactly what was causing that, and so our models aren't reproducing it

but one thing you can notice here, it is primarily in the ocean.

The other thing I can tell you - coming from the southern hemisphere-

it is totally absent in the southern hemisphere

This warming in the 1940's was a regional phenomenon,

largely in the North Atlantic.

It just happened to warm up the surface of the North Atlantic so much

you see it on the global average as well.

The warming we are seeing now, since the 1970's, is very different

in character, it is homogeneous right across the planet.

The Southern Hemisphere is warming up now.

It is a different characteristic thing so, although our models are not

capturing everything, we think they are capturing the basics.

There is another way in which we know that greenhouse gases

are causing the current warming.

Different causes of warming have different fingerprints in the atmosphere

This is a slightly complex plot, and I apologise that it is one of the

more technical ones.

What I am showing vertically here is a slice through the atmosphere

from the surface where it has 1000 millibars of pressure up to the

stratosphere. This is going up from the surface

well up to into the stratosphere.

This is going latitudinally from the North Pole, 90 north, to the South Pole

This is a slice through the atmosphere showing you

where the heating comes from - from different sources.

Down here in the bottom right is what we need to explain the

observations. This is what solar would do.

It's a very different pattern to what we need for the total.

This is what volcanoes do, they come in transiently

and then they go away again. This is what ozone does.

Greenhouse gases is a large part of the pattern. If you don't have

this in, you cannot reproduce the pattern of warming in the atmosphere

and across the surface of the planet.

There are fingerprints that we use as well.

Putting all the stuff together, our authors decided that this

was the best way of capturing in a single sentence -

our Attribution Statement as we call it:

Most of the observed increase in global average temperatures

since the mid-Twentieth Century are very likely - more than 90% -

due to the observed increase in greenhouse gas concentration

If you tease that apart it is actually a very carefully constructed

statement and it probably took about three or four attempts to

argue it past our authors. Our authors are very finicky people,

they don't say things lightly.

Time to move on to the future a little bit.

How do we address the future?

As scientists we can't tell you how much carbon dioxide is going to

be emitted in 2050 or something like that.

We have to de-couple a little bit, assumptions about what people

are going to do, from what we know in our climate model.

We know the climate system will be behaving in the same way

in 2050 as it does today, the laws of physics don't change.

We don't know how much people are going to react to the climate

change issue, we don't know what the emissions are going to be.

We take a range of different scenarios, and the upper panel here is

showing a higher, a middle and a lower emission scenario.

These were constructed around 1999 / 2000 and they are all

considered "business as usual" because in the course of this century

lots of different things could happen,

and we could choose to live very differently.

The lower case here is a world which is very much

an information and service economy

The higher end is very much an economy driven entirely in terms

of material possessions, that has implications,

particularly in the latter part of the century.

You can see that for two of these scenarios, the emissions actually

peak, at least these carbon dioxide emissions peak this century.

The two lower ones have moderate population projections for this

century the higher one has a high population projection but that also

underlies the emissions here. We have to assume that stuff.

I will draw your attention to the feint grey line here

the dark black is the actual fossil fuel emissions up to 2006

and the feint grey line adds on our best estimate of emissions

to the atmosphere due to deforestation.

If you look at where that feint grey line is, it is actually at the upper

end of the range of what we projected back in 2000, 7 or 8 years ago.

We might expect emissions are running high,

so the human factor is running at the high end.

The lower panel just shows you what the CO²

concentrations would do for those things.

Notice the blue curve here the emissions peak this century

and then start to come down

The carbon dioxide concentration does not come down, doesn't even

flatten out, until right at the very end of the century.

The reason is that it is not just enough to stop the emissions

increasing, you have to bring emissions down to the point where the

natural removal process of taking carbon dioxide out of the atmosphere

every year are larger than what you emit.

You have to get that balance to be negative again before you

bring the amount in the atmosphere down.

That doesn't happen until quite a long time after the peak in emissions.

That's why the blue curve goes on rising until 2100.

Just a bit of advertising I guess, we had a huge buy-in

from the science community in putting this report together

I don't want to even think about what the super computers time

cost for this project, but it is probably tens of millions of dollars went

into this, it may even be a hundred million dollars.

We had fourteen modelling groups, we had eighteen of the top

one hundred super computers working on this stuff

23 different computer models. There are tera bytes of information

available on the public website, if you want to register to get access to it.

This is what the temperatures look like

and you can see the red, green and blue.

There is another curve at the bottom there, that I did not talk very

much about in the previous slide, but it is what would happen

if we had kept the atmosphere constant.

This is just a physics test, it's obviously not realistic.

If we kept the atmosphere constant from year 2000 onward and we hadn't had any

change in the amount of greenhouse gases or aerosols from then on

We still get a bit of warming, but for those "business as usual" cases,

we are getting a warming of about .2 degrees per decade, sort of

independently of their structure or what happens, that

seems to be very hard to change.

It's the warming further out that does now depend on what we to choose to do,

where we get to by the end of the century.

Definitely we have the ability to influence that,

and that's what we need to think about.

Then there is the commitment run. If we kept everything constant

at a year 2000 atmosphere we would still get a warming of .6.

It is in the pipeline, it is unavoidable.

If you think you might operate on the basis of "lets just drive the climate

up to where it starts to become uncomfortable and then we'll stop",

that's not realistic for lots of reasons.

One of them is, there is all this warming in the pipeline,

it is still going to come at you.

The second thing is, you can't suddenly stop anyway because there's

a lot of other commitment based on our energy infrastructure,

the way we produce energy and things like that.

That actually probably has a bigger effect even than this .6.

I am going to come back to that later on if I don't run out of time.

No-one lives at the global average. The land is warming more than

the oceans. And here we see the projections. That's going to continue.

The land warms more than the oceans. The high Arctic warms even more

again. This shows the projection on a map: the darker reds being warmer

and the purple colour for the very high temperatures.

If you average over the whole planet you have got a warming here

of 2.8 degrees - It is at mid range scenario that we showed previously -

in the end of the century. You see the Arctic is warming by six degrees.

Large areas of North America and Europe are warming by 3 degrees,

more three and a half.

When people talk about living with two degrees, just remember in

your head, what happens in a particular place - it may be rather more,

and in some places maybe rather less. Ireland doesn't do too badly here.

New Zealand also doesn't do too badly, we go out at the global mean.

But we have to live on a planet with another seven or eight billion

people and we cannot afford to ignore what they are experiencing.

Rainfall will change as well. We know a lot more now than we did

6 years ago about the nature of the rainfall patterns, and we know that

one of the dominant effects, not the only one, is you just

increase the amount of water vapour in the atmosphere, because

everything is warmer, the surface is warmer,

there is more evaporation going on.

The rainfall patterns are very largely controlled on the large scale

by atmospheric circulation, where air diverges, comes up off the surface,

and diverges away from itself, you get drying, and where air comes

together, and brings water vapour together, you get stuff coming out.

You see a pattern very much like this already in terms of where the

precipitation is occurring, the rainfall band in the Tropics, rainfall

in the North, and you get these dry Sub-Tropics and this is the change.

If we want to summarise the change very simplistically, we say

the wet areas get wetter and the dry areas get dryer.

So for people who are already maybe stressed by drought,

it is not going to get better, it is going to get worse.

For people who are experiencing floods,

it is not going to get better, it is going to get worse.

We see this seasonal pattern reinforcing that view: when it is wet, it is

going to get wetter and when it is dry, it's going to get drier.

I want to say something about extremes.

If you think of the temperature in Dublin in November, and you

measure it year after year after year.

you would expect there to be some average, and you would expect

a distribution around that average, because not every year is the same.

These distribution curves tend to look like this blue curve here.

It tends to be a bell shaped curve.

Then you can think of how to use this. This is departure from average

along the bottom and this is the frequency with which it occurs

You can then think of in the terms of the future, the probability of it

occurring again in the future, so

people like engineers designing river systems, bridges or things like that

tend to have ideas of what a one in a hundred year flood or something

like that is. They are collected from statistics like this.

Here we characterise these curves by their width.

The standard deviation, as its called in statistics, and you can see

I have marked there just a little blue area is on the wings of this curve

what a 1:40 year event might look like, that far away from the average.

But now if the average changes and you get a shift -

lets say we shift everything one standard deviation -

then it’s the wings that really get altered very significantly

That one in forty year event is now a one in six year event,

you can go on out: a one in 100 year event becomes a 1 in 20 year event.

This is the nature of why extreme events are potentially so important

for the impacts you will see from climate change.

I could show you an lot of other stuff,

but I don't have it in this presentation,

to show that a one standard deviation shift in something

like the average temperatures in Europe or some other part of the world

isn't an exaggeration.

For those "business as usual" scenarios,

you're going to see a lot more than a one in standard deviation shift.

I am showing you a conservative view of how extremes can change.

Some of the texts we had in our report just stressed that increases

in heavy precipitation and drought will increase.

We understand the physics of that very well.

Even in places that are getting drier, they are going to get what rainfall

they do get in more intense events.

That can create a lot of problems.

As you may know, if you get a lot of dry conditions, and then

you suddenly get a huge amount of rain, the soil doesn't soak it up.

It all runs straight off, we have seen that happen in New Zealand.

The risk of the 2003 type European heat wave is already doubled,

due to the increase of greenhouse gases,

and it is obviously going to go further.

Extreme summer temperatures at least 20 times

more frequent by the end of the century.

Extreme events are going to be the thing that our children and

grandchildren are going to live with. To some extent, it is unavoidable.

I want to talk about another area of major concern for scientists,

that is Ice sheets and Ice shelves.

This is a picture of what is called the Larsen B ice shelf, a little while

after it broke up in 2002. This is an ice shelf, it is floating ice.

It was typically 300m thick in most places.

It disappeared in thirty days, with no warning as far as we knew.

Things must have been happening to it under the surface,

that people didn't know about, but it was staggering to see it happen.

That was floating ice and floating ice, when it melts,

doesn't raise sea level because it displaces the same amount of water.

Its a physics thing -

But the land based glaciers in Antarctica,

(where the Larsen B ice shelf is, I bet I didn't say that before)

once that floating ice shelf had gone,

these things sped up, and instead of flowing slowly into the ocean,

they started flowing quite a lot faster.

Some of them then actually slowed up again,

so there are a lot of dynamics suddenly going on,

some of which we are tracking,

and hopefully we are tracking the most important stuff.

Places where the ice shelf did not disintegrate, glaciers didn't speed up at all.

But that actually revolutionised the way people thought about the

role that ice shelves are playing.

They assumed that ice shelves didn't have any effect

on glacier outflow from either Greenland or Antarctica.

We now know that was too simplistic.

Similar things are happening in Greenland.

Let's talk about Greenland for a minute.

We are seeing the area of the Greenland plateau, that melts every summer -

so the surface goes liquid every summer - increasing dramatically.

The yellow line is the average boundary of what melts here,

you can see it is from 1979 to 2005.

The things on the coastal side of that would melt,

on average, during that period, inside they wouldn't.

But the red is showing what actually happened in 2005.

It is now melting very much more.

It is not the run off from that stuff, that matters quite so much, it is

whether it is changing the structure of the ice sheet.

This is a picture that was made famous by the US climate scientist

James Hansen, he publicised this a lot.

(I wouldn't have liked to have taken this photograph.)

It is in Greenland, it is showing liquid water

coming down these channels on the surface, and pouring down

what is called a moulin, which is a shaft going down to bedrock.

We are getting liquid water going down to the base, where the ice is

sitting on the rock, and potentially mobilising the movement of the ice.

Our models have always assumed that we have a block of ice,

flowing under its own weight, off the plateau in Greenland

and falling into the sea slowly.

The prospect now is maybe that is a flawed way of looking at things.

When you get to the edge of these things, and the ice starts

to crack and fissure as it goes over turning points on the rock underneath,

and then start to approach the coastline,

it might be more like Swiss cheese than a solid block.

There are potentially lots of tunnels and fissures and caverns and

things down there and, to the extent that they have liquid water in them,

you can see they're potentially going to mobilise the ice movement

a lot more than we are assuming in our model.

This was something we couldn't really deal with in our report this year.

I want to show how this played out for our estimates for sea level rise.

I am beginning by showing you what we said six years ago

We have a broad range of sea level

because we knew there were a lot of uncertainties.

This is how sea level was going to rise over the century.

In six years later, we are now putting the numbers like this.

We actually think we know things like the thermal expansion part

of this stuff much better, because we are using

much more sophisticated models of the ocean,

and we have much more data on which to calibrate them.

When we look at the total, we have to say, well there is a big unknown.

The bottom line statement we are making now, is we give you

a value, and then we say but larger values cannot be excluded,

because our understanding is too limited.

And there is nothing in the literature that we could use,

even in all those 5000 literature references,

to come up with a better number. This is new stuff.

Thermal expansion continues for many centuries.

The other key point to keep in mind

is that the last time the planet was significantly warmer than it is now

was in the previous warm period,

we go back past the previous ice age 125,000 years ago.

That wasn't caused by people, it was caused by nature, but

it gives us an analogue.

We know that sea level was four to six metres higher.

We know that was largely due to depletion of the Greenland ice sheet,

and to some extent probably the Antarctic ice sheet as well.

So if we have any influence on the temperature of where we are

going now, it might be an idea to try to avoid that.

But I want to say something else about this too, which is that

it took us a long time to come up with a way of saying we didn't know something,

and in retrospect thinking back my colleagues,

sort of grappling with the language here,

I realise that as physical scientists,

we always want to tell you what we know about,

what we measure, we like to give you numbers,

and to admit that we can't - is hard.

The aim of the Framework Convention on Climate Change is to

avoid dangerous anthropogenic interference of the climate system.

For me as a scientist, when we cannot tell you what is happening,

it is dangerous.

So if you are waiting to get there, I think it is later than you think.

I think we are there in some respects.

Here is another way of looking at where we might want to go to,

and where we might want to keep below.

The EU has set that as a political target, keeping warming below 2 degrees.

It is actually 2 degrees from a pre-industrial level,

so when I put it back on this plot that I showed you earlier,

you have to note that my zero here was actually the 1990's,

and we have already had half a degree of warming

from pre-industrial to get here.

So this line is actually at 1.5,

but it is where the EU political target is to try and avoid danger

but now look at what we've got.

We've got this committed warming of .6 in the pipeline,

we've got warming going on at .2 degrees per decade,

and we've had nearly a decade since 2000 already.

How long is it going to take us to turn around our energy system?

Maybe 30 years, okay that's another .6.

You add these things up, and you realise that

keeping to this level is almost impossible now.

If we really, really tried very hard, we might just achieve it.

If we are really, really fast, but the bus has almost left town

and we didn't get on it.

If we'd started ten years ago it would have been much easier.

So don't give up, because we certainly don't want to

go up to the very high temperatures, and we can still avoid them,

but recognise that we are going to have to learn

to adapt to a different climate.

So to summarise I'm telling you the evidence of change is unequivocal.

I'm telling you that now we are far enough down a pathway,

that the climate in the 21st century will be different

from anything we've seen in human civilisation,

that goes back 10,000 years or so.

We know this climate change is different from the past natural changes,

like the warming 125,000 years ago,

because it is happening faster than it did in the past,

and we know we are doing it from simple physics,

and it's going to effect us.

So, we've got to now sit ourselves on a mould of managing the unavoidable,

and avoiding the unmanageable.

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