The ECO-ACTIVE guide to the Scienceand Impacts of Climate Change in Jersey

Planning andEnvironmentDepartment

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ACKNOWLEDGEMENTSIn the autumn of 2007 ‘Planet Guernsey - Towards a Sustainable Future’ waspublished under the editorship of Dr. Andrew Casebow. This was an accomplisheddocument giving in-depth information on the critical issue of climate change froma wide range of expert contributing authors yet it was highly readable and waswarmly welcomed by members of the public.

The success of ‘Planet Guernsey’ made it clear there was a demand for wellresearched locally relevant scientific information and it inspired this publicationwhich explores the science of climate change and its impacts on Jersey. It is withour utmost appreciation that we acknowledge the assistance and co-operation ofAndrew Casebow and his co-authors, in producing this ‘sister-volume’.

We have also turned to a number of local experts to interpret many of the subjectareas specifically for Jersey. Biographies of all of the contributing authors areprovided at the end of this publication and represent a wide breadth of local andnational experience in this field.

SUMMARYAccelerated climate change as a result of human activity is an urgent issue. Wehave reached a turning point that requires an immediate response which policymakers and planners must consider without delay for the sake of futuregenerations. The most recent evidence announced by leading global climatescientists at the Copenhagen climate change summit in March 2009 led to theconclusion that the situation is ‘even worse than feared’ and it is becomingincreasingly difficult to avoid catastrophic climate change.

‘Turning Point’ examines the science and impacts of climate change on Jersey.The first part of this publication examines natural and human influences whichchange the Earth's climate. It shows that climate change, in the form of a globalwarming trend, is now firmly established as fact by all leading scientists, by theindependent International Panel on Climate Change (IPCC) and is endorsed bythe Royal Society. Furthermore, a large part of the warming can be confidentlyattributed to human influences, while sophisticated computer model forecasts allindicate the warming will continue for centuries, with debate confined to thedegree of warming.

The second part examines the impact of the warming in Jersey, looking at the likelyimpact on the island's industries, its flora and its fauna, but just as important at theattendant rise in sea level which threatens our low lying coastal areas. ‘Globalwarming’ is happening now and this publication examines what it is likely to meanfor Jersey.

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FOREWORD

The spectacular development and economic growth of the Western World in the 19th and20th Centuries was matched by a parallel growth in the use of energy. One has driven theother. Consider for instance heating, lighting, travel and transport, food production,manufacture of goods and materials, and electrical devices from carpet cleaners tocomputers. Without access to large quantities of energy our society across the developedworld would grind to a halt.

Unfortunately this technological miracle has significant consequences. We are only justbeginning to understand and appreciate the major impacts they will have on our world andthe future world of our descendants. Our thirst for energy has been quenched by theburning of vast quantities of fossil fuels - including oil, gas and coal - all of which producecarbon dioxide (CO2) along with other pollutants during combustion. Evidence compiled bythe Intergovernmental Panel on Climate Change (IPCC) is overwhelming. The IPCCattribute the observed changes in the Earth’s climate predominantly to the over productionof carbon dioxide.

The IPCC is an independent scientific body and is a key player in the understanding andappraisal of the evidence of human-induced climate change. Their role is to assess the‘latest scientific, technical and socio-economic literature produced worldwide relevant tothe understanding of the risk of human-induced climate change, its observed and projectedimpacts and options for adaptation and mitigation’ .

In Oslo on the 10th of December 2007 the IPCC and Albert Arnold (Al) Gore Jr. wereawarded the Nobel Peace Prize:

"for their efforts to build up and disseminate greater knowledge about man-made climatechange, and to lay the foundations for the measures that are needed

to counteract such change".

This publication aims to present the scientifically endorsed facts on the way the world’sclimate is changing and to interpret what that means for Jersey. Only by fully understandingthe problem and its effects can we commit to action to minimise (mitigate and counteract)the effects of climate change.

Tackling climate change is the most important challenge facing humankind in the 21stCentury and can not be ignored. This appraisal clearly highlights the urgency with which weneed to act.

Senator Freddie CohenMinister for Planning and EnvironmentApril 2009

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CONTENTSCONTENTSCHAPTER 1CHAPTER 1 -- A CHANGING WORLD A CHANGING WORLD

Natural Climate ChangeNatural Climate Change1.11.1 How Does the Atmosphere WorkHow Does the Atmosphere Work 881.21.2 How the Earth’s Natural Cycles Affect ClimateHow the Earth’s Natural Cycles Affect Climate 10101.31.3 What Else Influences the Climate?What Else Influences the Climate? 1212

Evidence of Natural Climate VariabilityEvidence of Natural Climate Variability1.41.4 Long Term Climate ChangeLong Term Climate Change 14141.51.5 The Present Interglacial PeriodThe Present Interglacial Period 16161.61.6 How has Jersey’s Climate Changed Over the Last 500,000 years?How has Jersey’s Climate Changed Over the Last 500,000 years? 18181.71.7 Jersey’s Changing Landscape Over the Last 20,000 yearsJersey’s Changing Landscape Over the Last 20,000 years 2020

CHAPTER 2CHAPTER 2 -- THE HUMAN INFLUENCE THE HUMAN INFLUENCE

The Science of Global WarmingThe Science of Global Warming2.12.1 An Introduction to Climate ChangeAn Introduction to Climate Change 24242.22.2 What are ‘Global Warming’ and the ‘Greenhouse Effect’?What are ‘Global Warming’ and the ‘Greenhouse Effect’? 2626

A Changing World?A Changing World?2.32.3 The Intergovernmental Panel on Climate ChangeThe Intergovernmental Panel on Climate Change 28282.42.4 How do we Measure Global Climate Change?How do we Measure Global Climate Change? 30302.52.5 How has Global Climate Changed in Recent Times?How has Global Climate Changed in Recent Times? 3232

Jersey’s climate through the 20th CenturyJersey’s climate through the 20th Century2.62.6 Have we Observed Changes to the Island’s Climate?Have we Observed Changes to the Island’s Climate? 34342.72.7 Is the Local Marine Climate Changing?Is the Local Marine Climate Changing? 3838

Alternative Climate Change TheoriesAlternative Climate Change Theories2.82.8 Are Greenhouse Gases Really to Blame?Are Greenhouse Gases Really to Blame? 4040

CHAPTER 3CHAPTER 3 -- LOOKING TO THE FUTURE LOOKING TO THE FUTURE

Global Climate ForecastsGlobal Climate Forecasts3.13.1 How do we Predict Climate ChangeHow do we Predict Climate Change 46463.23.2 What will Happen in the Future?What will Happen in the Future? 48483.33.3 Can we be Confident in our Predictions?Can we be Confident in our Predictions? 50503.43.4 How will the Global Climate Look in the Future? ShortHow will the Global Climate Look in the Future? Short--TermTerm 52523.53.5 How will the Global Climate Look in the Future? LongHow will the Global Climate Look in the Future? Long--TermTerm 54543.63.6 What Impacts will Climate Change Cause GloballyWhat Impacts will Climate Change Cause Globally 5656

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RRegional Climate Forecastsegional Climate Forecasts3.73.7 How do Models Predict Regional Change?How do Models Predict Regional Change? 58583.83.8 How will Jersey’s Climate Look in the Future?How will Jersey’s Climate Look in the Future? 6060

CHAPTER 4CHAPTER 4 -- IMPACTS ON THE ISLAND IMPACTS ON THE ISLAND

Global FalloutGlobal Fallout4.14.1 How will Climate Change Influence the Economy?How will Climate Change Influence the Economy? 64644.24.2 International Climate Change AgreementsInternational Climate Change Agreements 66664.34.3 Impacts on the Developing World?Impacts on the Developing World? 6868

IndustryIndustry4.44.4 How will Climate Change Affect Jersey Businesses?How will Climate Change Affect Jersey Businesses? 70704.54.5 The impact of a Low Carbon Economy on the Finance SectorThe impact of a Low Carbon Economy on the Finance Sector 72724.64.6 Climate Change and the Rural EconomyClimate Change and the Rural Economy 74744.74.7 The Future of FisheriesThe Future of Fisheries 78784.84.8 Tourism: Will the Industry Benefit or Suffer?Tourism: Will the Industry Benefit or Suffer? 8080

BiodiversityBiodiversity4.94.9 Climate Change and Regional BiodiversityClimate Change and Regional Biodiversity 82824.104.10 How will Climate Change Alter the Island’s HabitatsHow will Climate Change Alter the Island’s Habitats 84844.114.11 How will Climate Change Affect the Island’s SpeciesHow will Climate Change Affect the Island’s Species 86864.124.12 Plankton, a Climate Change indicator?Plankton, a Climate Change indicator? 88884.134.13 The effects of climate change on Intertidal speciesThe effects of climate change on Intertidal species 9090

HealthHealth4.144.14 Human Health in a Changing ClimateHuman Health in a Changing Climate 92924.154.15 Insects and Climate Change: What a Pest!Insects and Climate Change: What a Pest! 94944.164.16 A Changing Climate for Animal HealthA Changing Climate for Animal Health 96964.174.17 Climate Change, A Growing Problem for Plant Health?Climate Change, A Growing Problem for Plant Health? 9898

InfrastructureInfrastructure4.184.18 Sea Level, of Rising Importance?Sea Level, of Rising Importance? 1001004.194.19 Our Future Water Supplies in a Changing ClimateOur Future Water Supplies in a Changing Climate 102102

WHERE DO WE GO FROM HERE?WHERE DO WE GO FROM HERE? 104104

STATES OF JERSEY CONTRIBUTORY AUTHORSSTATES OF JERSEY CONTRIBUTORY AUTHORS 106106EXTERNAL CONTRIBUTORY AUTHORSEXTERNAL CONTRIBUTORY AUTHORS 107107

Image Credit : http://www.jersey.com/images

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CHAPTER 1CHAPTER 1A CHANGINGA CHANGINGWORLD...WORLD...

Image Credit: NASA, Image of the Day GalleryImage Credit: NASA, Image of the Day Galleryhttp://www.nasa.gov/multimedia/imagegallery/iotd.htmlhttp://www.nasa.gov/multimedia/imagegallery/iotd.html

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The media has for sometime now been awashwith climate change‘buzzwords’ such asgreenhouse gases,carbon footprint andglobal warming.

However, beforeaddressing theinfluence that humanshave had on theatmosphere, it isimportant tounderstand the basicsof how the climate hasbeen operating forhundreds of thousandsof years without theincreased levels ofgreenhouse gases thatwe now observe.

This chapter addressesthe issue of naturalclimate variation.

It considers the differentfactors that ‘force’ theclimate. These includethe position of the sun,the absorption of thesun’s energy andinteractions that go onwithin the atmosphereitself.

It goes on to examinethe contributory factorsthat have resulted inlong term variations inthe global climate andhow they have relatedto changes in thelandscape andcoastline of Jersey.

The climate is forever changing, with a multitude

of factors that influence its behaviour over time.

Historical records show there have been

numerous global, as well as local, shifts in the

climate. This chapter identifies why these

changes have occurred. To understand how

climate may change in the future, it is first

important to determine how and why it changed

in the past.

CHAPTER 1 — A CHANGING WORLD

Natural Climate Change

1.1 How Does the Atmosphere Work?

1.2 How the Earth’s Natural Cycles Affect Climate

1.3 What Else Influences the Climate?

Evidence of Natural Climate Variability

1.4 Long Term Climate Change

1.5 The Present Interglacial Period

1.6 How has Jersey’s Climate Changedover the Last 500,000 years?

1.7 Jersey’s Changing Landscape Overthe Last 20,000 years

CHAPTER 1 - A CHANGING WORLD

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Natural Climate Change

1.1 HOW DOES THE ATMOSPHERE WORK?James Le Ruez

THE ATMOSPHERE

The atmosphere is constantly transportingheat. This is easily observed on the island - inthe winter a northerly wind will feel coldwhereas a southerly wind will be milder. Thewind is bringing the air masses from the northand south respectively and as it does theheat contained within the air is redistributed.But how do winds work on a global scale?

Hot air rises and cold air sinks. Therefore, dueto the different intensities of sunlight, warmair will rise at the equator and sink at thepoles (Box 1a). However, this ‘single cellsystem’ is a simplified version of reality - thewarm air that rises at the equator does nottravel all the way to the poles before sinking.A three cell system has been suggested byscientists (Box 1b) which takes into accountthe spin of the Earth which causes winds atthe surface to be deflected to flowdiagonally. Winds (and currents) are shiftedto the right in the northern hemisphere andleft in the southern hemisphere.

To fully understand climate change, it isessential to appreciate how our climate haschanged in the past. Why are there icecaps at the poles? Why is it stormy in Jersey inwinter and why is it fine in summer? Theanswers lie with the Earth’s energy andradiation balance - how the Sun’s energy isabsorbed and redistributed around theworld.

As the Earth is spherical the Sun’s energy isnot received equally at all points on thesurface. The nature of the atmosphere andthe angle of the Sun’s rays means sunlightreceived at the equator is much moreintense than at the poles. It is this higherintensity of sunlight at the equator that resultsin the equatorial region being warmcompared to the poles.

However, it is not always hotter in the southcompared to the north. This is because theenergy from the Sun is absorbed andredistributed around the globe. To maintaina balanced temperature across the globeheat is transferred north and south by windsand currents.

Box 1(a) In this simplified case the globe is madeentirely of land and does not rotate. The airwithin the equatorial region heats up,becomes less dense and rises. In contrast, coldair at the poles is dense (and heavy) so staysnear the surface and spreads as it hasnowhere else to go. This creates a ‘cell’ wherethe heating and cooling of the air massescreates a wind at the surface transporting coldair from the poles toward the equator.

(b) In reality the warm air that rises at theequator does not have enough energy to betransported all the way to the poles. Therefore,three ‘cells’ are set up in each hemisphere withair rising at the equator and 60°N anddescending at the poles and the tropic ofcancer. The rotation of the Earth and thedistribution of land and sea shifts these north/south winds to their diagonal directions.

(a)

(b)

Image Credit: http://www.fas.org/irp/imint/docs/rst/Sect14/ect14_1c.html

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The sun’s influence gives the atmosphere itsoverall structure but many other factors mustbe considered. Land and oceans absorbheat differently. Land warms and cools veryquickly, therefore large landmasses are veryhot in summer and very cold in winter. Incontrast, oceans take a long time to heat upand cool down and therefore do not showsuch large temperature variations. This meansthat the theoretical three cell circulationpattern is disturbed and differs seasonally.

For instance, the heat of Russia in the summercauses air to rise over the continent (lowpressure) but in the winter it causes air to cooland sink (high pressure). However, the threecell circulation is still the major influence onlocal climate in most locations (see Box 2).

THE DEEP OCEANS

As water is significantly more dense, it can‘store’ far more heat than air. This means,when water moves around the Earth, ittransports a lot more heat than the air. Theoceans are therefore the most importantmechanism in maintaining a globallybalanced climate.

Water, like air, becomes more dense whencold; it therefore sinks at the poles. This coldwater at the bottom of the ocean doesn’tget heated by the Sun - but it does mix withthe warmer water above. It is forced to movearound the ocean due to differences in thedensity of the surrounding water. This processdrives the global deep water oceancirculation (Box 3).

Ocean currents are also influenced by thewater’s salinity as this effects water density.For example, in the Mediterranean the hotclimate evaporates large amounts of waterfrom the ocean. This leaves warm water withhigh concentrations of salt which is thereforerelatively dense. This water sinks and ispushed into the Atlantic Ocean despite itsrelative warmth.

A CHANGING WORLD

Box 3Global ocean circulation is key intransporting heat to differentregions of the Earth. The top fewmetres of the ocean transport asmuch heat as the entireatmosphere. As the oceans areon average 3.7 kilometres deep,they are responsible for themajority of heat transportationaround the globe. At the surface,ocean currents are drivenprimarily by wind and do notmove in a similar pattern to deepocean currents.Image Credit: Woods Hole Oceanographic Institution,

http://www.whoi.edu/oceanus/viewImage.do?id=47168&aid=20727

Box 2We can see the influence of the globalcirculation locally. This tree overhangingthe 5 Mile Road in St Ouen has grownleaning north-east as a result of theprevailing south-westerly winds. Jersey islocated around 49°N and Box 1bhighlights how these ’westerlies’ are anexpected part of the global circulationat the Island’s latitude.

Image Credit: James Le Ruez

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The current stage of the cycle may meanthat the world is nearing the end of itscurrent ‘interglacial period’ and withoutglobal warming mean temperatures mighthave started to fall. However, temperaturechange would be very small compared tothe large increases of temperature that arelikely to be caused by global warming.

2. Axial Tilt—The angle of the earth’s orbit tothe sun

The Earth’s tilt (Box 2) at the Equator variesfrom between 21.6° and 24.5° degrees in aperiodic manner of about 41,000 years. Thetilt today is about 23.5°. These changes inthe earth’s tilt affect the severity of theearth’s seasonal changes and theseseasonal changes are much moreapparent towards the North or South Pole,away from the Equator.

One suggestion is that the lower axial tiltmight promote the growth of ice sheets. Thereason for this is that warmer winters couldsupport greater atmospheric moisture andthen heavier snowfall. Summertemperatures would be cooler, leading toless melting of the winter snowfall, andgreater annual accumulation.

The cycle of ice ages and shorter interglacialperiods (and the changes of climate withinthe ice ages), and even seasonal changes,are caused by cyclical changes in ourplanet’s movement around the sun. They arecalled Milankovitch Cycles after theastronomer who first calculated them, andthere are three main cycles: -

1. Eccentricity—The Earth’s Orbit around theSun

The Earth's orbit around the sun is not a circle(Box 1), but an ellipse. The effect of this is tochange the distance that the Sun’s shortwave radiation must travel to the Earth in thedifferent seasons.

At the present time the orbit is at its leastelliptical, which means that a difference ofonly 3% occurs between the extremes, butthis still means that the earth receives 6%more solar energy in January than it does inJuly each year. When the Earth’s orbit is mostelliptical (on a cycle of about 100,000 years),then the seasonal difference in solar energywould be 20-30%. This changing amount ofreceived solar energy results in substantialchanges in the Earth’s climate, and in thechange from glacial periods (ice ages) tointerglacial periods.

1.2 HOW THE EARTH’S NATURAL CYCLES AFFECTCLIMATE

Box 1The eccentricity, e, of the Earth’s orbit around the Sun is given by the equation e2 = 1— y2 /x2 . The term ‘aphelion’ means furthest point and ‘perihelion’ the nearest point from theSun.

Image Credit: Planet Guernsey, 2007

Andrew Casebow and Chris Regan

Natural Climate Change

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3. Precession

‘Precession’ (Box 3) is the Earth’s slow wobbleas it spins on its axis, which causes a change inthe timing of the annual equinoxes. The axis ofthe Earth wobbles from pointing towardsPolaris (the North Star) to pointing towards thestar Vega. Each cycle of this ‘wobble’ takes23,000 years.

When the Earth’s axis is pointed towards Vegathe Northern Hemisphere will experiencelonger winters because this hemisphere isfurthest from the Sun. This results in greaterseasonal contrasts. At present the Earth isnearest to the sun very close to the wintersolstice.

Conclusion

These variables are important because mostof the world’s landmasses are in the Northern

A CHANGING WORLD

Box 2The axial tilt of theearth’s orbit to thesun varies.Currently it is at anangle of 23.5°.

Image Credit: Planet Guernsey and Chris Regan, 2007

Box 3The Earth’sprecession, or slowwobble as it spins, iscaused by thedifferentialgravitational forcesof the Sun andMoon on the Earth.Currently it is veryclose to the wintersolstice whichmeans our wintersare generallylonger andsummers shorter.

Image Credit: Planet Guernsey and Chris Regan, 2007

Hemisphere. When the Northern Hemispheresummers are coolest because they are furthestfrom the Sun (due to greatest orbitaleccentricity and precession) and the wintersare warmest (due to minimum tilt), snow canaccumulate and cover large areas ofnorthern America and Europe. At present onlyprecession is in the glacial mode, whilst tilt andeccentricity are not favourable to theformation of glaciers.

Even when all the cycles favour the formationof glaciers, the increase in winter snowfall anddecrease in summer melt is barely sufficient totrigger glaciation, and not sufficient todevelop large ice sheets. The growth of icesheets requires the support of a positivefeedback loop. One such ’loop’ might be thefact that ices masses reflect more of the sun’sradiation back into space, thus cooling theclimate and allowing glaciers to expand.

12

Natural Climate Change

day and slowly release it at night. As aconsequence urban areas can be warmer(by as much as 1°C)than the countryside.

There are so many different factors thatinfluence the climate and the daily weatherthat it is impossible to forecast the weatheror climate with 100% accuracy. The difficultyof accurately forecasting climate isdiscussed further in Chapter 3.

FEEDBACK EFFECTS

In addition to micro-climate influences,climate studies must also consider feedbackprocesses. In some systems, a certaininfluence will create a cyclical effect andreturn an impact back into the system.

Climate feedbacks can work to enhancean initial input (a positive feedback) orreduce it (a negative feedback). Box 2details three important feedbackmechanisms and explains why they may beimportant in a changing climate.

VOLCANOES

Volcanic eruptions have long beenrecognised as contributors to short termclimate. In the immediate aftermath of avolcanic eruption particles in theatmosphere act like clouds. Particles low inthe atmosphere have a life of only 1-3weeks. However, if the eruption is strongenough to send matter into the stratosphere

The Sun is the key driver of the Earth’s climateand the amount of energy received isdependant on astronomical factors. Thedistribution of this energy around the globecreates circulation patterns in eachhemisphere with the influence of land andsea causing regional circulation cells.

These regional patterns of high and lowpressure essentially determine the day to dayweather experienced on the ground. Forexample, British winters are generally eitherwet and windy or cold and dry, see Box 1.

MICRO-CLIMATE

Numerous additional interactions can causechanges on a local scale. Some of these arepermanent and therefore generate a localclimate trend. For instance:

HILLS AND MOUNTAINS – Mountains or hillscan force air parcels upwards. Water vapourcools and condenses creating local cloud orrain ‘shadows’.

LOCAL WINDS – In the summer land heats upmore than the ocean. This causes air to riseover the land and sucks in air off the seacausing an onshore breeze. Such seabreezes are noticeable in late afternoon onlong coastal strips in warm climates.

URBAN EFFECT – In urban areas the densematerials making up the infrastructure (e.g.buildings and roads) absorb heat during the

1.3 WHAT ELSE INFLUENCES THE CLIMATE?James Le Ruez

Box 1THE BRITISH WINTERIn case (a) storms are crossing the Atlantic fromthe south west, creating wet weather.Temperatures are relatively mild as the air hasabsorbed heat from the warm ocean.

In case (b) the regional patterns work against theglobal circulation. The less intense low pressureand stronger high pressure diverts storms awayfrom the UK towards the Mediterannean orGreenland. The UK experiences dry, coldweather as the air masses arrive from the coldEurasian land mass.

(a)

(b)

Image Credit: Martin Visbeck, http://www.ldeo.columbia.edu/NAO

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(approximately 10km high) the aerosols lastfor 1-3 years. In both cases the aerosolsaffect the reflection of the Sun’s rays,reducing the amount of heat penetratingthe atmosphere and actually absorbingheat themselves. The culmination of theseeffects results in the warming of the middleof the atmosphere and cooling at thesurface.

Mt. Pinatubo erupted in the Philippines onJune 15, 1991, and one month later Mt.Hudson in southern Chile also erupted. Theircombined aerosol plume diffused aroundthe globe in months. The data collectedafter these eruptions show that mean worldtemperatures decreased by about 1°Cover the subsequent two years.

Volcanic emissions include CO2 but as weshall discuss later, account for less than 1%of the emissions due to human activities.Therefore they play only a minor role inatmospheric CO2 increases compared toother sources.

EL NINO

El Niño is a short term climate influence thatcan raise temperatures globally throughreleasing large amounts of heat from theocean to the atmosphere. A weakening ofthe trade winds and surface current allowsthe warm pool of water to spread acrossthe Pacific towards South America. El Niñooccurs as an event lasting several months,with no fixed cycle and intervals rangingfrom 2-7 years.

‘La Nina’ conditions occur when tradewinds converge at the equator causing asurface ocean current that pushes sun-warmed water into the Indo-Australasianregion. Off the coast of Peru nutrient richwater ’upwells’ from the deep to replacethat moving westward.

Despite the changes in ocean temperatureand atmospheric circulation beingconcentrated in the South Pacific, El Niñohas a warming influence on globaltemperatures. For example, it causestorrential rain and flooding in the Andeanstates and drought and water shortages inIndonesia. There is also a clear statisticalrelationship between El Niños andhurricanes / typhoons. The strengthening of

A CHANGING WORLD

Permafrost are areas of permanently frozenground. With increases in temperature somesuch areas are thawing. This results in methaneand other greenhouse gases trapped withinthis frozen land becoming released to theatmosphere.

Box 2FEEDBACK EFFECTSAlbedo is a measureof how reflective asurface is. A highalbedo surface (e.g.ice and cloud)reflects a lot of light.Small increases in ice at the poles results inmore sunlight being reflected, less surfaceabsorption and in turn more ice.

Cloud formation can stimulate a ‘negativefeedback’ process. In hot regions air risesand forms clouds which cause shade andcool surfaces down.

‘jet streams’ in the upper atmosphere by El Niñohas been proposed as a likely cause of the wetweather and flooding in the UK in the winter of2007/08.

El Niño is important within the climate changedebate as it has a warming influence on globaltemperatures. This means the warmest years onrecord tend to be linked to El Niños. Forexample, the anomalously high temperaturesobserved in 1998 (14.54°C, 0.52°C above the1961-1990 global average) have been attributedto global warming combined with an extreme 18month El Niño.

The El Niño phenomenon is very complex and it isunclear how it will be affected and thus go on toaffect climate change. However, it doesappear that the El Niño pattern is changing.

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Evidence of Natural Climate Variability

over the past 50 million years is clear, andparticularly the cold of the last 3 million years.

In the last million years, perhaps the peak ofthe present ice age, climate has also beenmost unstable with around 10 major glacialperiods of 100 thousand years duration. Theseglacial periods that we normally think of as‘ice ages’, each lasted some 80-90 thousandyears of cold conditions and 10-20 thousandyears of warmer conditions. In the last millionyears there have been very few times whenthe global temperature has been as warm asit is now, and in the last 11,000 years duringwhich human civilisation has developed.These three most pronounced warm periods,known as ‘interglacials’, occurred at around420, 330 and 125 thousand years ago.

Box 2 contains a graph showing the ratio ofoxygen isotopes for the last 500 thousandyears, and from them you can see thesequence of warm and cold periods followingeach other, with warm peaks at about every100 thousand years. In the diagram, warmperiods have odd numbers and one can seethat only numbers 5, 9 and 11, whichrepresent interglacial periods that occurred

We are living in an Ice Age. We don’t knowwhether we are in the middle or near theend, but it has been going on for around 30million years so far.

The last major ice age lasted 50 million years;from around 330 to 280 million years (Myr)ago during what geologists know as theCarboniferous and Permian Periods. Morerecently, between 100 and 50 million yearsago we can find little evidence of any ice atall, because the world was much warmerthen. The evidence for these deductions liesin the distribution of fossils. For instance, treesgrew in the far north (at a palaeolatitude of80° N) in warm periods, and sediments suchas ice-rafted gravel in deep-sea mud can befound much closer to the equator (at 35° N)during cold times.

The Earth’s climate has been anything butstable in the long term. Box 1 shows resultsfrom the most powerful climate indicator thatwe have, the ratio of oxygen isotopes inmarine shells, called foraminifera. Thisindicator combines the effect of ice volumeand temperature over the last 70 millionyears. The development of cooler climates

1.4 LONG TERM CLIMATE CHANGE

Professor Nicholas McCave

Box 1Ratio of oxygen isotopes (δ18O)in marine shells over the last 70million years.

Ice ages can be shown byoxygen isotopes measured inforaminifera - see illustrationabove.

Graph & Image Credit: Planet Guernsey, 2007Source: Ruddiman, W.F. 2001 Earth’s Climate:

Past and Future. WH Freeman, New York 465 pp

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at 420, 330, and 125 thousandyears ago, have values similar tothe present time (number 1).Number 2 is the last glacialmaximum that occurred about 20thousand years ago, with othereven-numbered glacial periodsrevealing that some glaciationswere less severe than others.

Therefore, it can be seen that mostof the time over the past 500thousand years the climate hasbeen much colder than it is at thepresent, and that the cold was onlybroken by brief warmer periods, orinterglacials. But even the warmperiods have not had stabletemperatures, as you will see in thenext article. Similarly, Box 3 showsthat the temperature in the last‘glaciation’ fluctuated and grewprogressively colder until the lastglacial maximum that occurredabout 20 thousand years ago, justbefore the climate warmeddramatically.

A CHANGING WORLD

Box 3The peaks and troughs in the diagram above referto Milankovitch cycles of 23,000, 41,000 and100,000 years.

Graph Credit: Planet Guernsey, 2007

Professor McCave says “we use data based on oxygen and carbon isotopes, skeletalchemistry, species abundances, organic molecules and physical properties of sediments asa basis for inferring past temperature, salinity, density, nutrients and flow speed of oceanicwater masses”.

An ice age is a geological period during which great glaciers and ice sheets extend from thePolar Regions towards the equator. Individual ice ages wax (glacial phases) and wane(interglacial phases) in strength. The present day climate is an interglacial phase within theQuaternary Ice Age, which began in the Northern Hemisphere about 3 million years ago andin Antarctica about 30 million years ago.

Box 2Ratio of 16 to 18oxygen isotopes in thelast 500,000 years.Cooler temperaturesresult in an increase,whilst warmertemperatures producea decrease in theratio. This process issignificant indetermining climatechange.

Graph Credit: Planet Guernsey, 2007Source ; Lisiecki, L.E. and M. E. Raymo, 2005 Paleoceanography, vol. 20 (PA1003)

Dec

reas

ing

oxyg

en is

otop

e ra

tio

Calendar age in years / 1,000s

1

2

3

4

59

68

7

10

11

12

16

Evidence of Natural Climate Variability

when it gives up its heat, but the extra freshwater made it too light, thereby slowing thesystem down.

Box 1a shows that ice and sediment recordsfrom Greenland and from a German lakeshow the same story; that a sudden dramaticfall in temperature occurred about 8,200years ago. The warmer temperatures seemto have returned after about 200 years,probably as the circulation returned tonormal interglacial conditions.

Since then there have been minor oscillationsof climate, shown by sediments excavatedfrom the Atlantic. This suggests 8 coolerperiods in the last 10 thousand years. Box 1bshows a higher percentage of sand grains(dropped from icebergs) which indicatescolder conditions.

The most recent of these warm/cooloscillations was the Medieval Warm Periodthat peaked between 1000-1200 AD, whenthere were vineyards in England as far northas Leicestershire; and the succeeding LittleIce Age that peaked between 1550-1800,when the Thames used to freeze over inwinter (see Box 1c). This temperaturefluctuation is clearly evident when tree-rings,that record the conditions when the tree wasgrowing, are analysed. From this it can beseen that at no time in the last 2,000 yearshas it been warmer than the present, andthat the current trend is taking globaltemperatures beyond the maximum attainedin the past half million years.We are entering uncharted territory.

Anthropologists have argued that therelative climatic stability of the past 10thousand years has allowed development ofmodern human civilisation, including thefarming of plants, the domestication ofanimals, and the building of cities. It wasonly in the past 25 thousand years that ourspecies Homo sapiens emerged as thedominant hominid with the decline of theNeanderthals. However, the period from 25to 11 thousand years ago saw huge climateshifts in the transition from full glacial (with icedown to the Isles of Scilly) to presentinterglacial conditions, with both majorwarmings and coolings; which was notfavourable for the establishment of stablehuman communities.

Then about 10 thousand years ago theclimate became relatively stable, withestimated global mean temperature shifts ofless than 1° C (compared with around 5° C glacial to interglacial change). There wasone ‘blip’ on this stable warm climate, thatoccurred about 8,200 years ago. This wascaused by the final collapse of theCanadian ice cap. This produced a suddendischarge of fresh water, that had gatheredin a vast lake as the ice melted, into theNorth Atlantic. It is thought that this suddeninflux of cold, fresh water caused atemporary weakening of the current systemthat brings warm waters from the Gulf ofMexico to north-western Europe. This system- The Gulf Stream and North Atlantic Drift atthe surface - depends on the water beingdense enough to sink in the Norwegian Sea

1.5 THE PRESENT INTERGLACIAL PERIODProfessor Nicholas McCave

17

A CHANGING WORLD

(a)

It may be salutory to reflect that whatever we do, the Earth will continue, with or withoutus. That is the lesson of the cataclysms recorded in the rocks.

As Ronald Wright has so pungently put it:

“If we fail - if we blow up or degrade the biosphere so it can no longer sustain us – Naturewill merely shrug and conclude that letting apes run the laboratory was fun for a while but

in the end a bad idea.”

Date, expressed in 1,000’s of years before present day

Perc

ent

PBox 1

(a): Temperaturesboth on theGreenland ice capand in a recordfrom a centralGerman lake showat least 1°C ofchange.

(b): A higherpercentage ofsand grainsindicate colderconditions.

(c): Temperaturevariations over thepast 1,000 years,clearly showing theMedieval WarmPeriod (peak 1,000-1,200) and the LittleIce Age (peak1,550-1800).

(b)

All Graphs Courtesy of: Planet Guernsey, 2007Sources : a) Von Grafenstein, U. and others 1998 Climate Dynamics, Vol 14 73 - 81b) Bond, G.C. and others, 2001, Science, Vol 294: 2130 - 2136c) Moberg, A. and others, 2005, Nature, Vol 453: 613 – 617

Time in Years (AD)

Tem

per

atur

e A

nom

aly

(°C

)

(c)

18

Evidence of Natural Climate Variability

systems; the pattern of river valleys isrevealed not least by the underwatercontours.

Each climatic cycle was represented inbroad terms by an Interglacial and Glacialperiod. During the latter the sea level wasmuch lower and the area around theChannel Islands was dry land. As the climatechanged and moved towards the maximumof the succeeding Interglacial so the sealevel rose worldwide as ice sheets meltedand water was returned to the oceans. Thevery last cycle of all, represented by ourpresent Interglacial high sea level, showedthe same rise from a very low level as in

There have been five major interglacialperiods during the past 500,000 years andthese are related to the astronomical cyclesdiscussed in Article 1.2. Each lasted in theorder of ten to twenty thousand years withthe four intervening colder periods of muchlonger duration.

Over the same period the whole area ofsouthern England, the Channel andnorthern coastal regions of France has beenundergoing a continuing, if somewhatirregular, uplift of the land of somewhereunder 10 cm per 1000 years; this uplift isthought to result from earth movementslinked to still continuing distant Alpinecompression and deep-seated movementsin the Bay of Biscay.

During the Interglacials the sea level wasapproximately at its present day height.However, the land that was at sea level 400thousand years ago is now some 30 to 40 mhigher, as a result of the uplift referred toabove. Just as now, that sea of 400thousand years ago had its share of pebblebeaches and wave cut platforms and theseare now found at heights approachingbetween 32 and 40 m JD (Jersey Datum) asat South Hill, St Helier.

Other raised beaches and platformsrepresent other Interglacials:

20 to 25 m (300 thousand years old) 500meast of St Clement's Church on the rise ofthe Grande Route de St Clement

15 to 18 m (200 thousand years old) atlocalities such as Le Pinacle, Les Landes,St Ouen

Just above the present high water markof spring tides (120 thousand years ago)e.g. Le Pulec, L'Etacq (Box 1).

What is noticeable is the long duration ofthe Glacial periods when sea levels werelow and the Channel Islands would havehad a much colder climate. At these timesthey would have been part of mainlandFrance and England for long periods.

The map in Box 2 is a coloured version ofone published by Sinel (1912) and showsthat beneath the sea around Jersey atthese times there was a land mass with river

1.6 HOW HAS JERSEY’S CLIMATE CHANGEDOVER THE LAST 500,000 YEARS? John Renouf

Box 1We can see evidence of changes insea level in the Island's recent geology.This example in a gully at Le Pulec, justabove the present high tide mark,shows a notch eroded and smoothedby the sea of about 120,000 years ago.This is filled with sea rounded pebbles atthe base overlain by angular stonesabove, termed 'head', formed duringthe last Glacial period.

19

previous cycles. Box 3 reveals this changethrough a series of maps spanning from18,000 years ago to the Present.We should remember that there areseveral uncertainties inherent in evaluatingthe scientific evidence of sea level rise. Asa result, there are a range of possibleoptions for the detail of sea level rise.Combined with these uncertainties arethose stemming from the use ofradiocarbon dating. The net result is thatthe dates attached to specific sea levelsshould be read with full awareness of theuncertainties involved, suggesting that aplus or minus factor of 500 years should bekept in mind for each.

A CHANGING WORLD

Box 3

18,000 Years ago.Sea level over 100m lowerthan today.At the height of the last glacialmaximum the seashore is wellout in the Western approachesand the Hurd Deep is a lake.

14,000 years ago.Sea level about 75m lowerthan today.As the great northern icesheets began melting the sealevel rose rapidly and will soonrejoin with the Hurd Deep.

About 11,400 years ago.Sea level about 50 metreslower than today.The Hurd Deep is now a deepin the sea. Sea level is risingrapidly at this time.

About 10,200 years ago.Sea level about 30 metreslower than today.Jersey remains attached to thecontinent but Guernsey,Alderney and Sark are now cutoff from France.

About 9,400 years ago.Sea level about 20 metreslower than today.Guernsey, Alderney and Sarkare now separating from eachother. Jersey will shortlyseparate from the continent.

Present time.Within the last 10,000 yearseach of the Channel Islandsand associated offshore reefshave separated.

Map redrawn from Sinel, 1912

This map highlights Jersey as part of theEuropean landmass during Glacial periods.

Box 2

20

Evidence of Natural Climate Variability

Channel Islands appear on the cusp of 5,000BC when the natural vegetation wasessentially the same as it would be at thePresent were it not for the modificationsengineered by peoples' activities since, suchas clearances for agriculture and otherpurposes. The temperatures at this time aregenerally taken to be 1° C warmer onaverage than now.

The early Neolithic is also interesting in thatthe still rising sea level was now close to thatof the present very low tide mark (Box 2) andrecords the time when Jersey was becominga true island separated from the adjacentFrench mainland; Guernsey had beenseparated several thousand years earlier.

Evidence of the climate that prevailed in theChannel Islands area towards the end of thelast ice age comes from a number oflocalities.

Of particular interest are the lowermost softsediments found when excavating for thedam in Queen's Valley. From here Dr RobertJones and colleagues have described acold, arctic climate with a low ground coverof herbs and shrubs, possibly with some birch,poplar and pine trees. The cold is confirmedfrom beetle studies suggesting about 9° C forthe average temperature of the warmestmonth (a modern figure is almost doublethis). The deposits are dated to the mid-11thcentury BC, the last very cold spell before theHolocene warmth truly set in. The sea coastwas still many miles to the west of the island.

The recent find by Dr Arthur Hill in 2001 of asingle mammoth tooth in silty sediments onthe foreshore off La Rocque is likely toindicate an even colder time severalthousand years before this when perhaps thevery last of the mammoths in our part of theworld were roaming the low plains that thensurrounded Jersey.

Alongside the changes in sea level of the last20,000 years there were also rapid changes inthe natural landscape of the Island. Theseare outlined in Box 1 and were followed by aperiod of rapid warming after 10,000 BC,approximately the technical end of the lastice age.

By and large, within approximately athousand years, a well established forest waswidespread, though quite open in character.Birch, hazel and pine were quite commonbut by 8,750 BC, the forest was much moreclosed and birch and pine formed a lesserproportion of the trees. Pollen bearingsediments are not common in Jersey over thisperiod and it is not until after about 6000 BCthat pollen and other plant material againbecomes abundant enough to deduce aquite detailed climatic history.

The absence of evidence over this period islikely to be related to increased rainfallscouring out valleys rather than depositingsediments . This record is fully documented inJones et al., 1990.

The first indications of Neolithic peoples in the

1.7 JERSEY’S CHANGING LANDSCAPE OVERTHE LAST 20,000 YEARS John Renouf

(a)

(b)

(c)

Box 1Changing Vegetation of the Island:a) 16,000 BC: Open, dry, steppe-liketundra is typical of the ChannelIslands' climate.b) 11,000 BC: Low scrub vegetationwith patches of open woodland is thenorm.c) After 10,000 BC: The birch, hazeland pine forests shown here is rapidlyreplaced by a mixed oak-hazelwoodland.

21

The time interval 5,000 to 1,000 BC wasdominated by a sea level that was still risingbut now interacting for the first time with thezone represented by our present coastalplains.

During this final rise of the sea to present levelsjust described, the tussle between land andsea resulted in the creation of the wedge ofsoft sediments that fill Jersey's low lyingcoastal plains. In many areas much of thesediment, anything up to ten or more metresin thickness, are fine sands and silts derivedfrom the interior of Jersey and brought downby the streams that drain the plateau. Beforethe sea level rose above that of the low tideof today, all this land-derived sediment wasmoved away from our present coasts downthe river system shown on the Sinel map (Box2, previous article). With the rise in sea levelthe silt became trapped between barriersand pushed up in front of the rising sea andthe old fossil cliffs backing the coastal plains.The scenario presented here is general innature, and varies almost infinitely in detail.

The rise of sea level was all but over duringthe first millennium BC as sea level reachedmore or less its present height though thetension between land and sea has continuedto exist down to the present day. An

understanding of the processes at workduring this long time span is crucial for theshaping of responses to any sea level rise wemay see in the future as discussed in Article4.18.

The feature of sand blowingcontemporaneously is found on manyarchaeological sites ranging from theMesolithic through to the Middle Ages andlater. Such episodes may reflect short term'weather' changes ranging over months oryears or may result from longer term climaticshifts. At Le Pinacle, the Bronze ageoccupation layers are in sand separated offfrom the Neolithic horizons below; an Iron Agesite off Broad Street, St Helier was overlain byblown sand. Particularly important, however,is the evidence from the Middle Ages whenserious wind blow and sea encroachment,associated with much increased storminess, isboth well documented for the 14th century. Itis further proven by such excavations as thosein the Hue Street/Old Street area of St Helier inthe early 1970s. This was part of the generalclimatic deterioration of the time moving intothe Little Ice Age. Later dune building,particularly on the island's east and westcoasts, testify to relatively lengthy periods ofwind blow.

A CHANGING WORLD

REFERENCES

The following articles werereferred to in Articles 1.6and 1.7 :

Jones, R.L., D.H. Keen, J.F.Birnie & P.V. Waton. 1990.Past landscapes of Jersey :Environmental changesduring the last ten thousandyears. Société Jersiaise,Jersey.

Jones, R.L., C.E. O'Brien &G.R. Coope. 2004.Palaeoenvironmentalreconstruction of theYounger Dryas in Jersey, UKChannel Islands, based onplant and insect fossils. Proc.Geol. Assoc., 115 : 43-53.

Renouf, J. & J. Urry. 1976.The first farmers in theChannel Islands: TheNeolithic in an insularenvironment. EducationDepartment, Jersey

Box 2An indication of how Jersey's coast may have looked in earlyNeolithic times as sea level approached the current low tidemark. A land bridge, perhaps mostly tidal, still connects Jerseyto the continent and coastal plains exist in our current inter-tidalzone.