20141105_RC

Source: Royal Court Theatre

URL: N/A

Date: 05/11/2014

Event: Chris Rapley: 2071

Credit: Royal Court Theatre, Chris Rapley and Duncan Macmillan, also many thanks indeed to Geoff Chambers for transcribing this

People:

• Chris Rapley: Director of the British Antarctic Survey, 1998-2007

Chris Rapley: I’m here to talk about the future. As a climate scientist it’s part of my job to explore what it might bring.

My career’s been unusually varied. It’s included developing rocket and satellite instruments initially to study the universe and the sun, but more recently to observe the earth, particularly its polar regions. It also included running the International Geosphere-Biosphere programme, that co-ordinates the activities of over ten thousand scientists in 75 nations.

I’ve run the British Antarctic Survey, and in that role have been to the Antarctic and the Southern Ocean many times. I was president of the international scientific body that co-ordinates research in the Antarctic and was one of the architects of the International Polar Year 2007 – 2008, an exercise by thousands of scientists from over sixty countries to build up a snapshot of the polar regions.

My work has enabled me to travel to parts of the planet visited only by a few, and to meet experts from all over the world, to see and assess things for myself.

As director of the Science Museum, I moved away from running research projects, and instead sought out ways for scientists and the public to discuss complex and controversial subjects.

Perhaps the most complex and controversial subject of all is that of our climate: if it is changing, in what way, and on what time scale. It’s an extremely emotive issue, and we’re all susceptible to bias and irrationality when confronting it. The issues are often oversimplified. It’s a subject of enormous complexity. The climate system itself is very complex, the most complex system we know of. There are gaps in our knowledge, and many scientific uncertainties, some of which are fundamentally unknowable. This makes it extremely difficult to predict precisely what the future holds, and to determine exactly what, if anything, we should do.

In addition there are economic considerations, political implications, and ethical questions that are not easily answered.

But decisions are being made on our behalf at various levels of government and we all need to be part of that process.

One of my current responsibilities as chair of the London Climate Change Partnership is to draw together organisations within the public, private and civil sectors to make our capital city the best prepared and most resilient in the world with respect to climate change.

On some issues, such as flood protection, our planning horizon extends forward one hundred years.

The future is also being planned for at the national and international level. In December next year, 196 nations will meet in Paris to agree on a course of action to respond to climate change. Their discussions will be informed by a detailed summary of the latest climate science. The decisions they make will affect us all. I’m here to communicate the results of the science, their implications, and the options we have before us.

A lot has changed in my lifetime. When I was ten years old, my mother gave me an atlas in which large areas of the Antarctic were marked "Region unknown to man." But in that same year, an unprecedented sequence of scientific and technological advances began to open up that continent and render my atlas obsolete. It was 1957, and the Commonwealth Trans-Antarctic Expedition embarked on the first ever crossing from coast to coast via the South Pole. At the same time, despite the ongoing cold war, 67 countries, including the USSR and Eastern Bloc nations, collaborated in the International Geophysical Year, a project to intensively study the Earth.

Many advances were made in oceanography meteorology, magnetism, and a host of other research fields. One of the greatest advances was in the Antarctic, where airborne surveys using ice-penetrating radar, revealed for the first time the staggering depth of the ice sheet – up to four kilometres deep – and began to map out the mountainous terrain that lay below. Then, on October the 4th 1957; the Russians launched Sputnik One, the first ever satellite. I helped my father set up a short wave radio set so that we could listen to Sputnik’s faint bleeps amongst the hiss and crackle of the static as it passed overhead. Only four years after Sputnik, Yuri Gagarin became the first human in space, and just twelve years later, on July the 20th 1969, Neil Armstrong and Buzz Aldrin stood on the moon.

By that time I’d trained as a physicist at Oxford, and was at home with my parents awaiting my degree results. We watched the blurry footage of the moon landing together on a murky black and white TV set.

A few years later, in 1971, I began my research career, designing and building my own rocket and satellite instruments to study the cosmos. I went on to work with NASA in America, designing and operating a satellite mission to study solar flares, explosive energy releases which occur in the sun’s atmosphere.

After six years, as we started work on a follow up project, I saw some data from another NASA pioneering satellite mission, called CEESAT. It was a contour map of the very edge of the Antarctic ice. Instead of looking away from the Earth, CEESAT looked back at it. It carried radar instruments that imaged and mapped the oceans and polar regions. It had the ability to map the ice sheet change, and over time to model its changes. I knew I had to be part of this.

For the next fifteen years I built up a research group specialising in the design and use of radar altimeters to map the polar regions from satellites. At the same time I was a member of the small group of scientists from across Europe working with the European Space Agency to develop their series of Earth Observation Satellites. This work culminated in the CRYOSAT satellite, which is operating as I speak, taking hundreds of millions of measurements of the polar ice with pinpoint accuracy and unprecedented resolution. Maps of Antarctica produced from CRYOSAT cover 96% of the continent. Very little of the region remains unknown to man.

It hasn’t just been polar research that has benefited from satellite technology. The advanced instruments available today allow us to probe and map the key components of the Earth – the atmosphere, the oceans, the ice and the land in unprecedented ways. For example, space radars are unaffected by cloud cover and darkness, and unlike human researchers on the surface, they continue to observe in the depths of the polar winter. Imaging systems can see details at the level of metres. Instruments of exquisite sensitivity can detect tiny changes in the Earth’s gravity that allow us to measure changes in the mass of the ice sheets and the oceans. We combine the space data with myriad measurements made from aircraft, ships, buoys, and a host of specialised instruments on the ground. By using computer models to bring together the data with our understanding of the underlying physical laws, we can begin to make sense of what we observe. This provides us with a grand perspective of the Earth System as a whole, its component parts, and the interconnections between them.

The component parts are: the atmosphere – the layer of gas surrounding the planet; the hydrosphere – the oceans, lakes and rivers; the cryosphere – the ice on land and sea, the snow and the permafrost; the lithosphere – the outer layer of rock that makes up most of the planet’s mass; and the biosphere – all living material, including us.

The system behaves in complex and often counter-intuitive ways, but the fundamental principles of it are quite simple. The component parts interact with each other, exchanging energy in ways that operate in an overall dynamic balance. Dynamic balance applies to many features of the system, such as the balance of carbon between the atmosphere, ocean, land and vegetation, or the amount of ice on land or water in the ocean. But it especially applies to the energy balance of the planet, meaning that over time, the amount of energy leaving the planet is equal to the amount entering it.

The primary source of energy is the sun. About a third of the solar energy is reflected away by clouds, haze, and the surface, and about a quarter is absorbed by the atmosphere. Over 90% of the remainder is absorbed by the oceans since they cover the majority of the earth’s surface, and the rest of the energy goes into the land and ice. More energy is accumulated in the equatorial regions than at the poles, and its the action of redistributing this energy that drives the circulation of the oceans and atmosphere.

Heat energy, radiated by the earth’s surface, is partially absorbed in the atmosphere by trace gases: water vapour, methane and carbon dioxide.

The interactions between the atmosphere, the oceans, and the ice on land and sea drive the natural variability of the climate. The system’s very responsive, and even a small change in one component can trigger a chain of consequences in the other parts. And when such changes alter the energy balance, the effects are felt throughout the entire system.

Such changes include variations in energy received from the sun, either from fluctuations in the solar brightness, or from small variations in the earth’s orbit and tilt, the changes in distance and orientation relative to the sun. They include increases or decreases in the earth’s reflectivity due to variations in the cloud cover or volcanic eruptions that inject haze into the upper atmosphere, or changes in the surface cover of snow or vegetation. And they include changes in the concentration of water vapour, methane, and carbon dioxide that alter the planet’s loss of energy to space.

Whenever one of these changes takes place, the climate system adjusts until a new energy balance is reached. Some changes are amplified, and an especially important effect occurs in the polar regions where, as highly reflective ice and snow melts, dark, heat-absorbing land or ocean are revealed beneath. This increases the rate of melting, and amplifies the warming.

Since the majority of the energy is absorbed by the ocean, any imbalance would be most observable in the hydrosphere. To detect an energy imbalance in the oceans we can analyse data from a worldwide system of ocean buoys known as the Argo floats. Over 3,500 of these have been deployed by thirty nations throughout the world’s oceans since the millennium. The instruments measure the temperature and salinity to a depth of 2,000 metres. We can combine their measurements with contemporary and historic data from ships and other systems of buoys to allow us to estimate the ocean’s heat content and its variations. Additionally, we can measure sea level, which rises as temperature increases, acting as a global thermometer. The history of global sea level can be constructed from studies of beach structures world-wide, from archaeological data – for example from the location and height of Roman-era harbours, all of which hold a record of past sea levels.

There’s also information from a world wide network of tide gauges, installed in harbours on coastlines around the world over a century ago to provide data on local tides for seafarers and civil engineers. The number of ERR installations has increased over the years to nearly 300 sites worldwide creating the official global ocean sea level network. More recently, over the last two decades, satellite radar altimeters have revolutionised sea level measurements. They provide almost complete ocean coverage and they have the ability to detect variations in the global mean at the millimetre level.

The combination of all these data shows that over the last several thousand years global sea level was virtually static. In the late nineteenth century sea level began to rise. Over the twentieth century the rate of rise averaged 1.8 millimetres per year. Over the last two decades, the rate of rise has increased to 3.3 millimetres per year. This may not sound much, but it indicates that the dynamic energy balance of the climate system has been disrupted.

To understand the implications of this imbalance, we have to put it in the context of geological time. Scored in the rock and ocean sediments of the planet is a record of the past, often patchy and indistinct, but a record nonetheless. When we investigate this record, we find that the world’s climate has varied on many timescales and for many reasons.

Little is known of the early history of the planet after its formation 4.5 billion years ago. We do know that the biosphere emerged as son as the physical conditions permitted, about 3.5 billion years ago.

Like other components, the biosphere interacts with the rest of the system, in particular the atmosphere, in complex ways. In the great oxidation which started about 3.2 billion years ago, living organisms began producing oxygen in substantial quantities by photosynthesis. This ultimately transformed the atmosphere to the oxygen-rich state that we experience today. Over the last 500 million years, the climate has varied between a warm state – much warmer than today – and a so-called ice-bound state, in which ice sheets formed upon both poles. Between 360 and 300 million years ago in the Carboniferous Period conditions of temperature and moisture supported the formation of vast swamp forests. Their vegetation decayed, and the gradually overlaying ice sediments compressed and baked, creating deposits of coal, oil and gas.

250 million years ago, in the age of the reptiles, the temperature of the planet was much higher than today, and so was the carbon dioxide content of the atmosphere. The age of the mammals began about 65 million years ago following an asteroid impact in which more than three quarters of all plant and animal species on earth went extinct. Life gradually recovered, while in the meantime the planet slowly cooled, and by about 34 million years ago, ice sheets were developed at the South Pole. The system then went through another warm phase, after which, about 20 million years ago, we entered the ice house world [?] we experience today. Over the last 3.5 million years, the ice sheets at both poles have waxed and waned, initially in a 40,000 year cycle, and more recently, over the past million years, a 110,000 year cycle, triggered by small variations in the shape of the earth’s orbit and its orientation to the sun. As the ice sheets wax and wane, they have a huge impact on global sea level. During the transition from the peak of the last ice age 18,000 years ago to the beginning of the current warm interglacial period the oceans rose 120 metres at a sustained rate of one metre per century – ten millimetres per year.

12,000 years ago, as the transition from the last ice age came to an end, the Holocene epoch began. Global temperatures stabilised. The climate since then has varied gradually by about a degree centigrade, with natural variations of no more than a degree. The Holocene has been an extraordinarily stable period. We find nothing else like it in the climate record. It is argued that this relative equilibrium has enabled our species to flourish, first establishing agriculture, then civilisation, and then the modern world.

But the equilibrium is delicate. There have been small variations which have had [inaudible] consequences. For example, over the Northern Hemisphere, between the tenth century and the thirteenth century, regional warmings of up to a degree centigrade took place [allowing the Vikings to establish] substantial settlements on Greenland. It was followed by a cooling from the sixteenth century to the nineteenth century known as the Little Ice Age, when the Thames was repeatedly frozen and the Viking settlements in Greenland vanished.

The climatic variations during the Holocene period have had significant ??? 21:50 impacts, but they were small compared with the changes that took place over the 110,000 year ice age cycle. During the latter part of the Holocene, sea level changes did not exceed 0.2 millimetres per year. In the context of this, the 1.8 millimetres per year observed last century, and the 3.3 millimetres per year we observe today are geologically significant. The current rate is approaching that which occurs during the transition from the ice age to [inaudible] a major climatic shift. And it’s occurring [during an?] interglacial at a time unrelated to the natural ice age cycle.

To understand this change in the hydrosphere, we can first look at the cryosphere, in particular the ice shelves. Ice shelves are platforms of ice hundreds of metres or sometimes even a kilometre thick that extrude on to the main ice sheet on land. Both the ice sheet and the ice shelf move towards the ocean. The ice sheet moves over land, and the ice shelf moves over the sea. When the ice shelf runs aground on the ocean floor, its movement is slowed, causing a build up of pressure in the ice sheet behind it. If ocean temperatures rise, the water warms the underside of the ice shelf, which then collapses into small sections – ice floes. As the ice shelf collapses, the pressure of the ice sheet behind is relieved, and the ice sheet itself flows into the ocean, raising sea levels as it does so.

In 1995 the most northerly ice shelf of the Antarctic peninsula collapsed. For the first time in thousands of years it was possible to sail a ship round James Ross Island which until then had been linked to the Trinity coast of the peninsula by the ice shelf. The Northern peninsula ice shelves had waxed and waned even during the Holocene so this event was not necessarily climatically significant. However, since then there has been a progressive southerly wave of collapses. The Larsen AI shelf in 1995, the Wilkins in 1998, Larsen B in 2002.

The Larsen B collapse was particularly significant since the evidence of sediment cores is that it had been in place since the last glacial maximum, 20,000 years ago.

In 2008 and again in 2009, parts of the Wilkins ice shelf, the largest on the peninsula’s west coast, collapsed. In two years it reduced to one third of its original size.

I flew over the Wilkins ice shelf in 2009 and looked out on the vast area of shattered ice. It looked like a broken window. The pilot, who’d been flying in the region for more than twenty years, said he’d never seen anything like it. In 1978 John Mercer, the US glaciologist with much Antarctic field experience, described how in a warming world we might see a successive collapse of ice shelves extending down the Antarctic peninsula. He suggested that this would be a warning sign of the more worrying sequence of events to come. The Antarctic peninsula connects an area of the Antarctic called West Antarctica, and the chief feature of West Antarctica is that its massive ice sheet sits on bedrock that is up to two kilometres below sea level. For this reason it’s called a marine ice sheet.

Mercer’s concern was that if the successive collapse reached as far as West Antarctica, the pressure of the warmer water at depth would lift the ice sheet, causing water to penetrate deeper and deeper below the ice, producing friction between the ice and the rock, and so leading to an unstoppable collapse. This would lead to a rise in sea level over time of many metres, since the total volume of ice in West Antarctica is equivalent to a six metre rise. As Mercer feared; the ice shelf collapses along the peninsula have occurred, and parts of the West Antarctic ice sheet are now starting to collapse. Disturbingly, in East Antarctica, the Topham glacier, which is also marine-based, is showing accelerating ice loss too, which no-one predicted. And in the Northern hemisphere, the satellite surface data show that the loss of ice from the Greenland ice sheet has increased by 600%, from 34 gigatons per year in the late 1990s to 215 gigatons per year just a decade later. One gigaton is a thousand million tonnes.

Greenland’s fastest flowing ice outlet, the Jacobshavn, glacier is now flowing in the summer at speeds of 17 kilometres per year, nearly 15 metres per day, the fastest rate of any glacier or ice stream that’s been recorded. This glacier drains about 7% of the ice sheet; about 35 billion tons of icebergs calve off and pass out to sea every year. It was one of these that is thought to have sunk the Titanic in 1912.

In addition to this ice loss in Antarctica and Greenland, satellite image data reveal that 90% of the world’s glaciers and small ice caps are shrinking. There’s evidence from some historical records that some glaciers, especially in Europe, began retreating as long ago as the mid-nineteenth century, probably in response to the end of the little ice age. But the satellite data show that the retreat globally has gathered pace over the last thirty years. By analysing variations in the earth’s gravity field due to the mass of the ice sheets in the ocean, it’s been calculated that at present the melting of the ice sheets and glaciers contribute to about half of the observed sea level rise. Apart from a small contribution from the human use of aquifers, the rest of the sea level rise is due to thermal expansion. The water is getting warmer.

We know that this warming isn’t due to the sun’s brightness increasing, because satellite instruments have been measuring the solar energy flux very accurately since the 1970s. We also find that the lower atmosphere and surface are warming, but the upper atmosphere is cooling. If the sun were the cause, the upper atmosphere would be warming too.

To understand what’s causing the ice to melt and the oceans to warm, we need to look at what’s happening to the atmosphere, in particular trace gases; water vapour, methane, and carbon dioxide. These gases are present in relatively small quantities in our atmosphere in comparison to nitrogen and oxygen, but they have a significant impact on the temperature of the planet. Water vapour, methane and carbon dioxide obstruct the loss of heat from the surface as it passes upwards. This effect, referred to as the greenhouse effect, causes the earth’s surface to have an average temperature of 15°C. Without it, the surface would be 15 degrees below freezing. Life as we know it would not be possible.

We can observe the change in atmospheric concentration over time by looking at data from ice cores drawn from the ice sheets and glaciers in Antarctica and Greenland. The ability to study these ice cores is regarded by many as the most important advance in earth science of the twentieth century.

Each year the snowfall creates a layer that compacts to ice and traps bubbles of the contemporary air. The deepest ice cores extracted from the Antarctic are more than three kilometers long, and contain a record going back 800,000 years. As the director of the British Antarctic Survey on one of my Antarctic trips in 2002, I visited the European drill site at a place called Dome C. I watched as a fine section of ice core nearly half a million years old was extracted from a depth of just under three kilometres. It took an hour to load the drill, a few minutes to drill the core section, and an hour to winch it up to the surface. There are offcuts, small chunks of the core which aren’t useful to science. I picked a piece up. As a scientist, I try to remain objective and dispassionate, but here I was in a part of the world that had fascinated me since I looked at that area marked “Region unknown to man” as a child, holding a piece of ice that had not seen the light of day since before the dawn of mankind. I listened to the air bubbles pop and crackle as the ice melted in the heat of my hand. I breathed the air coming out of it, air that was trapped at the time of freezing. By measuring this air, it’s possible to study the composition of methane and carbon dioxide over time. We then melt the ice and measure the ratios of different atomic isotopes in the water. This provides us with a history of global temperature. We can then study the relationship between trace gases and temperature.

The ice core data show an almost perfect match between the time curves of global temperature and atmospheric concentrations of carbon dioxide and methane. As temperature increases, carbon dioxide and methane are released from the ocean and by the biosphere, causing further temperature rises through their enhancement of the greenhouse effect. The opposite takes place during the cooling phase.

During each recent cold phase, when on average global temperatures have decreased by 5°C, the carbon dioxide concentration of the atmosphere has dipped to about 180 parts per million. In the warm phases it peaked at around 300 parts per million. This year, the carbon dioxide concentration of the atmosphere passed 400 parts per million. Take a deep breath. We’re the first human beings to breathe air with that level of CO2. It’s unprecedented in the recent record. The rise over the last century is already one hundred parts per million, the same as the natural change between an ice age and an interglacial warm period, but at a rate more than one hundred times faster. And it’s in the warm direction that increased concentration not experienced by the planet with certainty over the last 800,000 years, based on the ice core data, and probably over two million years of the geological record [?]

The atmosphere is warming because the global carbon cycle is being [inaudible].

The global carbon cycle consists of large annual exchanges between the carbon reservoirs, the atmosphere, the land biosphere, the lithosphere and the ocean. These exchanges occur as a result of a variety of chemical, physical, geological and biological processes.

For example, as plants grow on land and in the sea in the spring, they draw down CO2 which is later released as the green matter dies and decays. In the ocean, biological processes cause a fine rain of carbon to descend as sediments, where it becomes trapped and stored. Volcanic eruptions ultimately return atmospheric carbon dioxide to the atmosphere. Physical exchanges take place between the atmosphere and the ocean. The CO2 is absorbed into cold dense waters that sink to depths [?] and is released from areas where warmer water upwells. These exchanges are much greater in magnitude than our own carbon emissions, but prior to industrialisation they were in dynamic balance. In 1712, the invention of the Newcomen steam engine started a chain reaction of innovation, technology and science that spread across the globe, driven by a desire for profit and the pursuit of a better life. This revolution built the modern world. It’s been fuelled by cheap and accessible fossil fuel energy which had been accumulated over hundreds of millions of years during the carboniferous period, and stored underground as coal, oil and gas. Since the 1950s, population, GDP, fertiliser use, water use, the number of cars, airline travel, and many other human activities, have all increased in what’s been called the great acceleration.

This has led us to the point where we’re currently burning ten thousand billion tons of carbon per year, a figure that’s increasing at the rate of 2% every year. To date, we’ve burned an estimated 530 thousand billion tons of carbon. A quarter of the resulting carbon dioxide is being absorbed by vegetation on land, which has bloomed as a result, and just over a quarter by the ocean, which has become more acidic. The remainder will stay in the atmosphere for hundreds to thousands of years, because it takes that long for natural processes, mainly rock weathering, to draw CO2 out of the atmosphere.

Consequently, since the beginning of the industrial revolution, atmospheric concentration of CO2 has risen by 40%. Human impact on the planetary system has became so profound that many feel that we have irreversibly brought the climate stability of the Holocene to an end, and entered a new epoch, the Anthropocene.

The energy imbalance revealed by the ocean, confirmed by rising temperatures and loss of ice, is being driven by us, which is the unwitting result of our use of fossil fuels. To me, the evidence seems compelling. But since the implications are sufficiently profound, a deeper evaluation is merited.

To make such an evaluation requires a Gargantuan effort, and this is the task given to the intergovernmental panel on climate change, the IPCC.

The IPCC was set up in 1988 by the United Nations Environment Programme and the World Meteorological Organisation. Its job is to provide a comprehensive summary of the scientific data to inform the policy decisions of the United Nations Framework Convention on Climate Change.

This is an international treaty negotiated by 196 nations at the Earth Summit in Rio in 1992, and its objective is to stabilise greenhouse gas concentrations in the atmosphere at a level that will prevent dangerous human interference with the climate system.

The IPCC has three working groups. Working Group 1 reviews and assesses the physical science information relevant to human-induced climate change. Working Group 2 addresses the related impacts on people and the environment, and Working Group 3 focusses on the policy options – adaptation to and mitigation of human-induced climate change.

Since its establishment the IPCC has produced five assessment reports, approximately one every five years, each consisting of a lengthy technical report; an agreed summary for policy makers; which is scrutinised and agreed by representatives on behalf of the governments participating in the IPCC process. The most recent Working Group 1 report – the fifth – was released in September 2013. It’s arguably the most audited scientific document, and possibly the most audited document in history.

The work was led by 209 scientists who are regarded as world experts in their respected fields. They were supported by more than 600 contributing authors from 32 countries, and 50 review editors from 39 countries. Of the tens of thousands of publications sifted, more than 9,200 were cited. The authors responded to 54,677 comments from 1,089 reviewers worldwide, and the final text was approved by representatives of 196 governments. The full Working Group One technical report has 1,535 pages and weighs four and quarter kilos.

So what do they conclude? Concerning the atmosphere: each of the last three decades has been successively warmer at the earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, the 30 year period from 1983 to 2012 was likely the warmest in the last 1400 years. They add that the globally averaged combined land and ocean surface temperature measurements show a warming of 0.8°C over the period 1850 – 2012. They note that despite warming at or near the surface, the upper atmosphere has cooled, ruling out the sun as the cause. They note an increase in the frequency of heat waves and heavy precipitation events that have occurred in many regions since the 1950s.

Concerning the cryosphere, they report that the rates of loss of ice from the world’s glaciers and from the Greenland and Antarctic ice sheets have all increased dramatically, especially over the last 30 years. While – losses have increased globally by about 20%, the ice sheet losses have increased over that ten year period period by as much as 600%. They report that the summer sea ice extent in the Arctic decreased over the last 30 years at a rate between 9 and 14% per decade, and they say that this level of ice [inaudible] is unprecedented in the last 1450 years.

In contrast, winter sea ice extent in the Antarctic has increased slightly, at a rate of about 1.5% per decade. This is driven by changes in the Southern Ocean winds that have intensified in response to the climate energy imbalance.

Other evidence of warming is provided by the loss of Northern Hemisphere snow cover at a rate of nearly 12% per year in summer, and increases in permafrost temperatures too. The warming since the 1980s has been 3°C in parts of Northern Alaska, and up to 2°C in parts of Russia, where a considerable reduction in the extent of permafrost area [inaudible].

Concerning the hydrosphere, they report that ocean warming dominates the increase in warming stored in the climate system, accounting for more than 90% of the energy – between 1971 and 2010. Over the period 1993-2010 tle level of sea level rise is consistent with a 30% contribution of thermal expansion, 48% melting ice, and 13% increase in land water storage. They confirm that the ocean has absorbed about 30% of the cumulative anthropogenic carbon dioxide emissions, causing it to become progressively more acidic.

Last week, the IPCC released their overall synthesis report. This report states that warming of the climate system is unequivocal, and since the 1950s many of these changes are unprecedented over decades to millennia. The atmosphere and oceans have warmed, the amount of snow and ice has diminished, and sea levels have risen. It observes: in recent decades changes in the climate have caused impacts on natural and human systems on all continents and across the oceans. Impacts are due to observed climate change irrespective of its cause, indicating a sensitivity of natural and human systems to a changing climate.

On the causes of climate change, the IPCC say that [inaudible] cannot account for the observations. They add: "It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused ny the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together." They continue that the best estimate for human-induced contributions is similar to the actual warming observed. In other words, there is evidence that all the warming that has occurred since 1950 is due to human actions – due to us.

They conclude: "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greehouse gas emissions, which together with adaptation can limit climate change risks."

John Kerry, the U.S. Secretary of State, summarised the findings as follows:

“Boil down the IPCC report, and here’s what you find. Climate change is real, it’s happening now. Human beings are causing the transformation; and only action by human beings can save the world from its worst impacts."

The cut-off date for published material considered by the IPCC Working Group One was July 2013. But science never stops, and there have been some important results since. Evidence from the Argo floats shows that despite the fifteen year pause in the rate of surface atmospheric temperatrure rise, energy has continued to accumulate in the oceans unabated, with the prospect that some of this energy will be released to the atmosphere in future. New data from the CRYOSAT satellite show that the recent rate of ice [inaudible] from Greenland and Antarctica has doubled in just three years. Some experts have concluded that the loss of ice from the West Antarctic ice sheet is now irreversible, and that the rise by one or two metres in as little as a few hundred years. Based on a combination of scientific analysis, assessment of the impacts, and related value judgements, the nations negotiating under the [inaudible] of the United Nations Framework Convention on Climate Change have set a limit beyond which climate change would be dangerous. That limit is 2°C above the pre-industrial average. We’re currently at 0.8°C, and two thirds of that increase has occurred since 1980. In order to stay below the 2°C guard rail human carbon emissions have to drop to 50% of the current level by 2050, and thereafter drop to zero – nothing. This could mean leaving 75% of known fossil fuel reserves in the ground. They would become economically worthless.

The temperature at which the system will stabilise is determined by the total quantity of carbon we emit to the atmosphere and not the rate at which it’s emitted. So reducing carbon emissions to zero won’t lower the temperature. It will just prevent the temperature rising beyond the 2°C level. Temperatures will then remain at that 2°C level for a very long time, because CO2 remains in the atmosphere for hundreds of thousands of years.

This sets a limit on the total carbon we can burn. The IPCC calculates this to be 800 gigatons of carbon, and they estimate that we have already burned 530 tonnes of carbon. This leaves 270 gigatons for us to use. At our current rate, which is 10 gigatons of carbon per year, we only have 27 years left, after which time emissions are due to cease. Suppose we begin reducing our emissions next year and don’t exceed the overall 800 gigaton limit.Then CO2 concentration will stabilise at 450 parts per million. Temperature will take longer to stabilise, because it responds to CO2 concentration, but it will eventually stabilise at our guardrail of 2°C. The oceans will continue to warm, and the ice will continue to melt, so the sea level will continue to rise. It will take hundreds of years, but will eventually stabilise at the level, based on evidence from past warmings, some two to three metres higher than today.

If we leave it longer to start reducing our emissions we’ll have to reduce them more rapidly to avoid exceeding the overall 800 gigaton limit. Calculations show that if we leave it until 2020, only five years away, the subsequent reductions would have to be of the order of 6% per year, year on year, to stay within the 2°C limit. Now 6% may not sound much, but actual reductions in carbon emissions greater than 1% have only been associated with economic recession or upheaval. The UK conversion from coal to gas and the French conversion to nuclear in the 1970s and 80s produced reductions of 1% a year.

A 5% reduction was achieved in the Soviet Union when it collapsed. Japan recently achieved a 15% reduction when its nuclear power stations were shut down and demand fell following the Fukushima disaster.

The 6% annual reduction required is of global emissions. We in the developed world will have to reduce our emissions even more rapidly to accommodate growth in the developing world.

To achieve the necessary reduction of emissions will require a major collaborative effort on a global scale. It will require the greatest collective action in history.

In December 2015 196 nations will meet in Paris to forge a deal to put the world on the path to a maximum 2°C rise. The new agreement aims to obtain credible and fair emission reductions and legally binding commitments from all countries reflecting GDP, education potential [?] and contributions to past and future climate changes, with the most advanced economies making the most ambitious commitments. There’s justified cynicism surrounding next year’s meetings in Paris. These nations have been meeting for decades, and overall emissions have not yet decreased. However, there are hopeful signs from world leaders and governments, and a growing pressure on them from an increasingly informed populace. This year a million people around the world marched in various capital cities to demonstrate their concern. [?] Paris in 2015 President Obama has proposed to cut carbon emissions from electricity generation in the USA by 30% by 2030, and Secretary of State John Kerry has pledged to keep climate change front and centre of American diplomacy.

Despite not having signed up to Kyoto or Copenhagen, the USA is already on track to cut its emissions by 17% between 2005 and 2020.

China, partly driven by serious air pollution problems, has committed to cutting the proportion of energy it generates from coal and has set up pilot carbon markets and low carbon zones. In 2010 it set a national target for reducing the energy intensity of its GDP by 15%. Prime Minister Narendra Modi of India has committed to expand solar energy to provide electricity for 300 million of his country’s citizens who have no access to power at present. And the EU has agreed a package to achieve a 40% reduction in its domestic emissions. They aim to boost the use of renewable energy to 27% and increase energy efficiency by at least 27%.

The UK Climate Change Act passed in 2008 with cross-party support is the world’s first long-term legally binding national framework for reducing emissions, setting five-year carbon budgets to cut UK emissions by 80% by 2050.

Around the world almost 500 climate-related laws have been passed in 66 of the world’s largest emitting countries, and although the long history of negotiations by the United Nations Framework Convention on Climate Change is seen by many as a chapter of failures, Others argue it’s created the conditions in which national legislators and decision-makers have been able to take actions which have had a positive effect.

In 2005 the mayors of the world’s forty largest mega-cities including London met and [inaudible] leadership group, and these cities have a combined population of 297 million people who generate 18% of global GDP as well as 10% of global carbon emissions, and collectively they’ve taken 4,734 actions to tackle climate change, over three quarters of which have been implemented.

Many individuals have taken measures to reduce their own carbon climate related impacts by making changes in their personal, professional and public lives; installing solar panels; increasing the energy efficiency of their homes, vehicles and [inaudible]; by using public transport and avoiding unnecessary travel; by changing diet, and choosing to forego activities that generate emissions. They’ve encouraged changes to be made in their workplaces and they’ve written to their MPs. They’ve sought to educate themselves about the issue and to talk about it with their friends, families and communities.

But despite all these measures, global carbon emissions continue to rise. In 2013 they increased by 2.1% to reach ten gigatons of carbon per year, their highest value yet. Suppose we fail to take the action needed to stabilise [inaudible] to 2°C [?]. The IPCC Working Group I predict that by the end of the century we could have committed to more than a 4°C rise. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions with serious impacts on ecosystems and food and water supplies. Given that uncertainty remains about the full nature and scale of the impact, there’s no certainty that adaptation to a 4°C world is possible. A 4°C world is likely to be one in which communities, cities and countries would experience severe disruption, damage and dislocation, with many of these risks spread unequally.

The International Energy Agency’s 2012 assessment indicated that without certain mitigation action, there’s a 40% chance of warming exceeding 4°C by 2100, and a 10% chance of it exceeding 5°C. No nation would be immune to the impacts of that level of climate change. Our infrastructure was built for the climate system we inherited, and it’s not designed to cope with the climate system we’re provoking.

Our food and water supplies, housing, industry – our entire wellbeing and prosperity depends on access to energy, and our primary energy source at present is fossil fuel.

So we’re confronted with the need to totally transform the world’s energy system. At the same time, we need to ensure energy security, equity, sustainability, and growth.

The amount of carbon we emit is determined by four things: the number of people on the planet; the size of the global economy; the amount of energy it takes to power that economy; and the amount of carbon it takes to create that energy.

There’s nothing we can do about population, which continues to increase, albeit at a decelerating rate, and is projected by the UN to peak at about 9 billion later this century.

There’s little we can do to reduce the global economy. All governments are committed to increasing it, and in any case our prosperity and wellbeing depends on it.

So there are only two areas in which we can take action to reduce emissions.

The economy can become more energy-efficient and less wasteful. This can be achieved through energy [inaudible] and by changes in behaviour at a personal and societal level. Many policies are already in place, but haven’t got close to the reductions that we need.

Which leads us to reducing the amount of carbon we emit to generate energy.

This involves renewable power sources – wind, solar, biofuels, and nuclear.

Around the world, renewable power capacity grew at its strongest ever pace in 2013, and now produces 22 [inaudible] of energy. More than 250 billion dollars was invested in green generating systems in 2013, although the growth is expected to slacken, not least because western politicians are expected to reduce financial incentives.

But in China, authorities have set green energy as a strategic priority. Their aim is that it will account for more than half of China’s energy production by 2050. This explains why investors are increasingly confident in keeping their money on alternative energy.

The [inaudible] of wind [inaudible] and solar [inaudible] in China, India, and an array of smaller developing nations is starting to outpace that of the world’s richest nations. But in the UK, despite our best efforts to move to green, renewable and nuclear, coal and gas still provide about 70% of the energy to our grid, and more in transport. To achieve the necessary reduction in carbon emissions will require the invention and mass roll-out of new technologies which at this present moment do not exist.

However, my experience in the Science Museum, with a legacy of technical innovation on public display and [inaudible] in schools convinces me that on a finite planet human ingenuity is unbounded. My hope lies with the engineers, but the right conditions need to be in place for innovation to occur. I’d like to see governments, investors, and the engineering profession itself create the conditions for a massive effort of innovation and roll-out of new energy technologies that will make fossil fuel redundant. Energy which is cheaper and cleaner than fossil fuels. Once available, the markets will drive its exploitation. But progress is hard when other economic drivers inhibit the transformation. Fossil fuels are estimated by the International Energy Agency to receive subsidies of 500 billion dollars per year – six times the incentives to develop renewables.

I think back to the remarkable collaborative achievements of the International Geophysical Year culminating in the first satellite and the obsolescence of my childhood atlas of the region unknown to man that I would want to visit personally dozens of times. I look at my oldest grandchild who is now the age I was during that world-changing year. I tell her I think she should become an engineer. She will reach the age I am now in 2071. I try to imagine 2071, and then I find myself thinking what 4071 would be like, or 10071.

We’re all dependent on energy. Almost everything we do depends on it. By being here tonight, by travelling to this theatre, by using these lights, the heating, the amplification of my voice, we have contributed to the amount of CO2 in the atmosphere. There will be carbon atoms that were generated by this event that will still be in the air in 2071, in the air that my granddaughter will breathe. That’s our legacy.

Science can’t say what is right and what is wrong. Science can inform but it cannot arbitrate. It cannot decide. Science can say that if we burn another half trillion tons of carbon, the atmospheric content of CO2 will go up by another hundred parts per million, and that this will almost certainly lead to a warming of the planet greater than two degrees, with major disruption of the climate system, and huge risks to the natural world and human well-being. But it can’t answer moral questions, value questions.

Do we care about the world’s poor? Do we care about future generations? Do we see the environment as part of the economy, or the economy as part of the environment?

The whole point about climate change is that despite having been revealed by science, it’s not really an issue about science. It’s an issue about what sort of a world we want to live in, what kind of a future do we want to create?