>> TODAY ON "EARTH FOCUS," FROM MONITORING GLACIER MELT AND ARCTIC SEA ICE TO WHAT SCIENTISTS SAY CLIMATE CHANGE BORDER WITH CANADA AND THE COAST RANGE MOUNTAINS, LIES THE JUNO ICEFIELD.

>> TODAY ON "EARTH FOCUS," FROM MONITORING GLACIER MELT AND ARCTIC SEA ICE TO WHAT SCIENTISTS SAY CLIMATE CHANGE MAY MEAN FOR OUR FUTURE, COMING UP ON "EARTH FOCUS."

>> ON THE EDGE OF THE GULF OF ALASKA, STRADDLING THE ICY BORDER WITH CANADA AND THE COAST RANGE MOUNTAINS, LIES THE JUNO ICEFIELD.

THIS IS THE FIFTH LARGEST EXPANSE OF ICE COVERING THE PLANET AND IS THE SOURCE AREA FOR HUNDREDS OF GLACIERS.

THE JUNO ICEFIELD RESEARCH PROGRAM, OR JIRP, HAS BEEN STUDYING THESE MIGHTY RIVERS OF ICE SINCE 1946 TO BETTER UNDERSTAND HOW OUR PLANET'S NATURAL ENVIRONMENTS ARE CHANGING AND WHAT THIS MEANS TO OUR COMMON FUTURE.

>> AND ACTUALLY THERE'S A LITTLE BIT OF COMPLEXITY AS TO WHY WE USE GLACIER ICE.

>> I CAME HERE AS A SCIENCE STUDENT 23 YEARS AGO AND RETURNED TO WORK HERE THIS SUMMER AS A PART-TIME STAFF MEMBER.

LIKE OTHER JIRPers, AS WE CALL OURSELVES, THIS PROJECT LAUNCHED MY INTEREST IN THE NATURAL WORLD AND CONTINUES TO INSPIRE MY SCIENCE REPORTING.

EACH YEAR A GROUP OF SCIENCE RESEARCHERS CROSSES THIS VAST AREA LIKE I DID, GETTING A CHANCE TO LEARN HOW TO SURVIVE AND CONDUCT RESEARCH IN THIS, ONE OF THE MOST WILD CLASSROOMS IN NORTH AMERICA.

SUPPORTED AND STAFFED BY THE FOUNDATION FOR GLACIER AND ENVIRONMENTAL RESEARCH, THE JUNO ICEFIELD RESEARCH PROGRAM HAS SOME OF THE LONGEST-RUNNING GLACIAL CLIMATE RECORDS IN THE WORLD AND IS A TREASURE TROVE OF VALUABLE DATA ABOUT HOW OUR WORLD'S CLIMATE IS CHANGING.

I'M HERE AT CAMP 17 ON THE JUNO ICEFIELD, AND I'M GOING IN TO HAVE A QUICK WORD WITH DR. ANTHONY ARENDT.

HE'S FROM THE UNIVERSITY OF ALASKA IN FAIRBANKS, AND HE'S ONE OF THE GUYS WHO DESIGNED THE LATEST SATELLITE IMAGERY SYSTEMS FOR NASA TO UNDERSTAND THE MASS BALANCE OF THIS ICEFIELD.

>> GLACIERS RESPOND IMMEDIATELY TO ANY CHANGES IN CLIMATE.

THEIR VARIATIONS AND THEIR MASS ARE DETERMINED DIRECTLY BY HOW MUCH SNOWS FALLS ON THEM IN THE WINTERTIME AND HOW MUCH ICE AND SNOW MELTS AWAY DUE TO WARMER TEMPERATURES IN THE SUMMERTIME.

SO BY MONITORING GLACIER VARIATIONS, WE CAN UNDERSTAND A LOT ABOUT CLIMATE SYSTEMS, AND SO THEY'RE ONE OF THE FIRST SORT OF EARLY HALLMARKS OF CLIMATE CHANGE ON THE PLANET.

>> DR. ARENDT HELPS CREATE HIGH-RESOLUTION COMPUTER MODELS OF GLACIERS LIKE THIS ONE USING DATA FROM SATELLITES, AIRPLANES, AND DEEP SNOW PITS LIKE THESE TO DEVELOP A CLEAR PICTURE OF OUR FUTURE GLOBAL CLIMATE.

95% OF ALASKAN GLACIERS ARE MELTING AT AN UNNATURAL AND UNPRECEDENTED PACE.

>> GLACIERS ARE REALLY LARGE CONTRIBUTORS TO CHANGING SEA LEVELS.

YOU WANT TO BE ABLE TO QUANTIFY HOW MUCH WATER IS COMING OUT OF THESE SYSTEMS EVERY YEAR AND THEN USE THAT INFORMATION TO DEVELOP MODELS AND PREDICT IN THE FUTURE TO HELP POLICYMAKERS PLAN FOR POTENTIAL FACTS OF SEA LEVEL CHANGE IN THE NEXT 50 OR 100 YEARS.

>> SCIENTISTS LIKE DR. ARENDT COME HERE TO CONDUCT RESEARCH AND TO SHARE THEIR EXPERIENCE WITH THE YOUNG-AND-UPCOMING RESEARCHERS TAKING PART IN THE PROGRAM.

TO COLLECT THE GROUND DATA THAT SOPHISTICATED HIGH-TECH SCIENCE DEPENDS ON, STUDENTS HAVE TO CROSS VAST DISTANCES THROUGH THE ISOLATED HEART OF THE ICEFIELD.

IN ORDER TO TRAVERSE THE ICEFIELD SAFELY, WE TRAIN THEM EXTENSIVELY FOR THE DANGERS OF THIS RUGGED FIELD EXPERIENCE.

HERE AT CAMP 17, THEY LEARN ADVENTURE SKIING, SAFE GLACIER TRAVEL ON A ROPE, AND HOW TO RESCUE A COLLEAGUE FROM A CREVICE.

THE TRAINING EQUIPS AND INSPIRES THESE STUDENTS FOR A CAREER IN EXTREME ENVIRONMENTAL RESEARCH, COLLECTING DATA THAT THE GLOBAL SCIENTIFIC COMMUNITY DEPENDS UPON TO FURTHER THE UNDERSTANDING OF OUR CHANGING WORLDS.

>> IT'S JUST A USEFUL TOOL IN ITSELF.

>> FIRST OFF WE PRACTICE TYING KNOTS.

THAT WAS LIKE THE BASIS OF ALL THIS, AND THEN FROM THOSE KNOTS, THEN WE LEARNED DIFFERENT WAYS TO USE THE KNOTS ON A ROPE, WHICH THEN YOU LEARN HOW TO SKI WITH A ROPE TEAM AND WHAT TO DO IN CASE ANYTHING BAD HAPPENS ON A ROPE TEAM, LIKE A FALL INTO A CREVICE AND HOW TO SAVE A TEAM MEMBER THAT HAS FALLEN.

>> YAY!

>> AFTER SCIENCE AND SAFETY TRAINING AT CAMP 17, THE PARTICIPANTS START THEIR TRAVERSE ACROSS THE ICEFIELD, DOING FIELD WORK IN GEOLOGY, GLACIOLOGY, CLIMATE CHANGE, AND OTHER DISCIPLINES.

>> WELL, WHEN THESE PEOPLE COME OUT OF THE ICEFIELD AND EXPERIENCE THE GLACIAL ENVIRONMENT, BY MAKING MEASUREMENTS, THEY CAN SEE HOW THAT ECOSYSTEM IS CHANGING THIS YEAR AND IN YEARS BEFORE.

>> TO BE ON THE JUNO ICEFIELD IS A FANTASTIC EXPERIENCE FOR ME, AND PART OF A MAJOR PROGRAM THAT MONITORS MASS BALANCE OF AN IMPORTANT GLACIER, AND IN ADDITION, IT GIVES ME THE OPPORTUNITY TO TRY AND CONTRIBUTE TO THE SCIENTIFIC DEVELOPMENT OF YOUNG SCIENTISTS.

>> MASS BALANCE INDICATES THE HEALTH OF A GLACIER.

A POSITIVE MASS BALANCE MEANS THAT THE GLACIER IS GROWING.

A NEGATIVE MASS BALANCE MEANS THAT IT IS SHRINKING.

THE OLDER A MASS BALANCE RECORD IS THE MORE VALUABLE IT BECOMES.

LONG-RUNNING STUDIES PROVIDE A HISTORICAL AVERAGE AGAINST WHICH THIS YEAR'S DATA CAN BE COMPARED, SHOWING HOW THE CLIMATE HAS CHANGED AND WHAT MAY HAPPEN IN THE FUTURE.

>> THE MASS BALANCE DATA THAT'S BEEN COLLECTED BY THE JIRP PROGRAM IS AN EXTREMELY IMPORTANT RECORD BECAUSE IT GOES BACK AS FAR AS 1946, AND THERE ARE PROBABLY ONLY ABOUT 30 GLACIERS IN THE WORLD THAT HAVE BEEN MONITORED FOR MASS BALANCE FOR 10 OR MORE YEARS.

>> A GLACIER EXISTS HERE BECAUSE SNOW THAT FALLS IN THE WINTER DOES NOT MELT COMPLETELY IN THE SUMMER.

THE RELATIVE AMOUNTS OF SNOWFALL AND MELT REPRESENT THIS MASS BALANCE.

LIKE A POSITIVE BANK ACCOUNT, A POSITIVE MASS BALANCE INDICATES THAT THE GLACIER IS GROWING.

ON THE FLIP SIDE, IF THE GLACIER HAS LESS SNOWFALL AND MORE MELT, THE GLACIER BECOMES SMALLER.

SO HOW HAVE GENERATIONS OF SCIENTISTS COME TO GRIPS WITH THE ESTIMATION OF THE HEALTH OF THIS 3,900-SQUARE-KILOMETER ICE SHEET?

THEY DIG.

A LOT.

BY DIGGING MANY PITS LIKE THESE, SCIENTISTS LIKE DR. JASON AMUNDSON CALCULATE HOW MUCH MELTED ICE IS FLOWING INTO THE OCEAN.

>> WHEN THE GLACIERS ARE ACTUALLY IN RETREAT, THE ONE THING THEY DO IS THEY CONTRIBUTE TO SEA LEVEL RISE, BUT THEY ALSO AFFECT ATMOSPHERIC CIRCULATION PATTERNS, WHICH PROPAGATES DOWNSTREAM.

IT AFFECTS OTHER THINGS.

THE CHANGES IN THE AMOUNT OF FRESHWATER RUNOFF INTO THE OCEAN, WHICH WILL AFFECT THE OCEAN PROPERTIES, WHICH COULD AFFECT THE MARINE LIFE.

>> THE GLOBAL SEA LEVEL IS GOING TO RISE, AND IT WILL RISE BY VARYING AMOUNTS DEPENDING ON WHERE YOU ARE IN THE WORLD, AND THE CONTRIBUTION FROM GLACIERS IS LIKELY TO BE SIGNIFICANT.

>> DIGGING SNOW PITS HAS BEEN USEFUL FOR ALMOST 60 YEARS ON THE JUNO ICEFIELD, BUT WHEN THESE SNOW PITS ARE PAIRED WITH NEW GROUND-BREAKING TECHNOLOGIES, THE SCIENCE BECOMES EVEN MORE SUCCESSFUL.

SALVATORE CANDELA IS USING A POWERFUL GROUND-PENETRATING RADAR, OR GPR AS IT'S KNOWN, TO GET INFORMATION FROM THE VAST AREAS BETWEEN SNOW PITS USING THE PITS THEMSELVES AS A REFERENCE FOR HIS READINGS.

>> THE DIGGING OF PITS AND USING GROUND-PENETRATING RADAR REALLY TIES WELL TOGETHER.

SINCE I'M IMAGING WHAT'S IN THE GROUND AND THEY'RE ACTUALLY DIGGING IN THE AREA I'M IMAGING, THEY COMPLIMENT EACH OTHER IN THAT IF I HAVE A QUESTION ABOUT WHAT I'M SEEING ON THE RADAR, I CAN GO JUMP IN A 5-METER-DEEP HOLE AND ACTUALLY SEE WHAT IS THERE.

AND BY PAIRING THEIR VISUAL OBSERVATIONS WITH WHAT'S ON THE RADAR, IT ALLOWS US TO COME TO A MUCH STRONGER CONCLUSION ABOUT WHERE THE ANNUAL LAYER IS OR WHERE A SPECIFIC DENSITY CHANGE MIGHT BE THAT THEY'RE LOOKING FOR IN THE MASS BALANCE PROCESS.

>> BY DRAGGING HIS GPR SLED, NAMED THE BUMBLEBEE, AND USING THE PITS TO CALIBRATE IT, CANDELA IS HELPING CREATE A MUCH BETTER UNDERSTANDING OF THIS DYNAMIC GLACIAL SYSTEM.

THE RESEARCHERS ALSO MAP THE MOVEMENT OF THE ICE WITH GPS AND 3-D IMAGERY.

>> ...SUCCESSFUL?

>> I THINK WE'RE VERY SUCCESSFUL.

JERKING IT AROUND.

>> OK, SO I GRAB IT, AND I MOVE IT AROUND TO THAT.

WOW.

>> THEY EVEN GET DEEP UNDER THE ICE IN VAST COMPLEXES OF SUBGLACIAL CAVERNS TO CALCULATE HOW THE GLACIERS ARE MELTING FROM THE BOTTOM UP.

THE HUGE LLEWELLYN GLACIER IN CANADA IS MELTING FAST, EXPOSING MORE OF ITS SECRETS FOR RESEARCHERS BROOKE STAMPER AND MIRA DUTSCHKE TO DISCOVER, USING PHOTOGRAMMETRY AND ICE LENS MEASUREMENTS.

AS THE 2013 FIELD SEASON ON THE ICEFIELD COMES TO A CLOSE, WE MAKE OUR WAY NORTHEAST AND WALK OFF THE LLEWELLYN GLACIER THROUGH A DANGEROUS CREVICE FIELD.

>> WE'RE WINDING OUR WAY THROUGH THE CREVICES OF THE LLEWELLYN GLACIER.

EVERYONE'S MAKING THEIR WAY VERY CAREFULLY HERE BECAUSE THE GLACIER GETS A LITTLE BROKEN UP, BUT IT'S A BEAUTIFUL DAY, AND IT LOOKS LIKE WE MIGHT MAKE IT ALL THE WAY TO LAKE ATLIN.

>> WE STRUGGLE DOWN THROUGH THIS DUSTY AND BLOWING NEWLY UNCOVERED GROUND WHERE THE VAST LLEWELLYN HAS MELTED AND FINALLY WE MAKE OUR WAY DOWN THIS LONG VALLEY TO LAKE ATLIN.

HERE WE'RE PICKED UP BY A BOAT AND START DECIPHERING THE DATA AND WORKING IT INTO THE SCIENTIFIC LITERATURE, WHERE RESEARCHERS AROUND THE WORLD CAN USE IT TO FINE TUNE THEIR CLIMATE CHANGE PREDICTIONS.

FROM THE GLACIOLOGICAL AND ARCTIC SCIENCES INSTITUTE ON LAKE ATLIN, BRITISH COLUMBIA, THIS IS JEFFREY BARBEE REPORTING FOR LINK TV.

>> GLACIERS ARE NOT THE ONLY THINGS MELTING.

SO IS ARCTIC SEA ICE.

JUST HOW FAST IS THE SEA ICE MELTING?

RESEARCH SCIENTIST JULIENNE STROEVE IS WORKING WITH THE NATIONAL SCIENCE FOUNDATION TO FIND OUT.

>> I KNOW THE IMPORTANCE OF SNOW AND ICE IN HELPING REGULATE THE PLANET'S TEMPERATURE, IT'S ONE OF THE REASONS I WENT INTO STUDYING SNOW AND ICE BECAUSE IT'S VERY IMPORTANT TO OUR CLIMATE SYSTEM.

AND I DON'T THINK IT REALLY WAS UNTIL ABOUT 2002, 2003 THAT WE STARTED TO REALLY START PAYING ATTENTION TO WHAT'S HAPPENING IN THE ARCTIC, BECAUSE BEFORE THAT WE WOULD HAVE, YOU KNOW, WE'D HAVE LOW SEA ICE IN THE 1990s AND THEN IT WOULD BE FOLLOWED BY A HIGH SEA ICE YEAR, BUT WHAT STARTED HAPPENING IN 2000 IS YOU'D HAVE A LOW SEA ICE YEAR AND ANOTHER LOW SEA ICE YEAR, AND IT JUST KEPT HAPPENING AND HAPPENING YEAR AFTER YEAR.

AND THAT WAS THE THING WE HADN'T SEEN BEFORE, AT LEAST DURING THE LAST SORT OF 50 YEARS OF DATA COLLECTION.

AND THEN WHEN 2007 HAPPENED, WHERE YOU HAD 26% DROP FROM THE PREVIOUS SEPTEMBER IN 2006, AND EVERYBODY WAS LIKE, WHAT IS GOING ON?

'CAUSE NOBODY EXPECTED THAT LARGE OF A DROP.

IT TOOK EVERYBODY BY SURPRISE IN THE SCIENCE COMMUNITY.

THE RATE OF DECLINE RIGHT NOW OVER THE LAST 3 DECADES IS ABOUT 14% PER DECADE, AND THIS IS ACTUALLY FASTER THAN MOST OF OUR KIND OF MODELS ARE ACTUALLY CAPTURING TODAY.

THESE PROJECTIONS OF ICE-FREE DATES OF, LIKE, 2050 TO SOMETIME BEYOND 2100, IT LOOKS LIKE IT COULD HAPPEN A BIT SOONER, SO LIKE 2030 MIGHT BE A MORE REALISTIC DATE AS TO WHEN WE MIGHT SEE NO SEA ICE IN THE SUMMER IN THE ARCTIC.

YOU KNOW, BASICALLY EVERYTHING ON THE PLANET'S CONNECTED, AND THE ARCTIC IS SORT OF THE BIG REFRIGERATOR FOR OUR PLANET.

IT HELPS KEEP OUR PLANET A LOT COOLER BECAUSE, AS YOU KNOW, SNOW AND ICE REFLECT MOST OF THE SUN'S ENERGY THAT COMES IN DURING THE SUMMER PERIOD, SO IF YOU REMOVE THE SNOW AND YOU REMOVE THE ICE, THEN THE LAND CAN ABSORB THAT HEAT FROM THE SUN OR THE OCEAN CAN ABSORB THE HEAT FROM THE SUN AND WARM UP FURTHER AND AMPLIFY THE WARMING IN THE ARCTIC FOR EXAMPLE.

ALL OF OUR WEATHER SYSTEMS OR LARGE-SCALE WEATHER PATTERNS ARE DRIVEN BY THAT TEMPERATURE DIFFERENCE BETWEEN THE EQUATOR, WHICH RECEIVES MOST OF THE SUN'S ENERGY, AND THE POLAR REGIONS, WHICH RECEIVE VERY LITTLE OF THE SUN'S ENERGY.

BUT IF YOU CHANGE THAT DIFFERENCE IN THE TEMPERATURE BETWEEN THE TWO REGIONS, YOU CHANGE THE SPEED OF THE LARGE-SCALE WEATHER SYSTEMS THAT MOVE AROUND THE PLANET.

AS YOU CHANGE THE TEMPERATURE GRADIENT, THESE WEATHER SYSTEMS START TO MOVE MORE SLOWLY THROUGH OUR ATMOSPHERE, AND YOU CAN GET MORE EXTREME CONDITIONS SUCH AS DROUGHTS AND FLOODS THAT JUST LAST LONGER IN A PARTICULAR REGION BECAUSE THESE WEATHER SYSTEMS ARE MOVING THAT MUCH SLOWER.

AND SO THERE IS A CONNECTION BETWEEN WHAT HAPPENS IN THE ARCTIC AND WEATHER IN THE LOWER LATITUDES.

AND WE KNEW THAT IF THE PLANET STARTED TO WARM AND YOU START MELTING SNOW AND YOU START MELTING ICE, THEN YOU'RE GONNA HAVE THIS SORT OF FEEDBACK EFFECT THAT'S GONNA AMPLIFY THE WARMING BECAUSE YOU'RE GONNA WARM UP.

YOU'RE GONNA MELT MORE SNOW.

YOU'RE GOING TO MELT MORE ICE.

IT'S GOING TO FURTHER WARM EVERYTHING UP AND MELT MORE AND MORE SNOW AND ICE, SO YOU HAVE THIS REALLY VICIOUS POSITIVE FEEDBACK.

SO WE KNEW THAT THE ARCTIC WAS VERY SENSITIVE TO INCREASES IN TEMPERATURE, AND IT'S RESPONDING LIKE YOU WOULD EXPECT IT TO AS THE TEMPERATURES HAVE WARMED, SO IT IS SORT OF AN EARLY-WARNING SYSTEM.

WE DID EXPECT CHANGES TO HAPPEN FIRST THERE BEFORE EVERYWHERE ELSE IN THE PLANET.

IF YOU LOOKED AT THE FACTORS THAT WE TENDED TO USE TO EXPLAIN PAST LOW SEA ICE YEARS, AND THOSE FACTORS REALLY WEREN'T WORKING ANYMORE, SO IT WASN'T NECESSARILY A CERTAIN WEATHER PATTERN OR, YOU KNOW, A CERTAIN TEMPERATURE PATTERN THAT WAS CAUSING IT.

THERE'S SOME SORT OF BACKGROUND FORCE THAT WAS HAPPENING ON THE ICE COVER THAT WE, YOU KNOW, WERE TRYING TO FIGURE OUT WHAT THAT WAS.

WHEN I STARTED LOOKING AT THE CLIMATE MODEL AND COMPARING THEM TO THE OBSERVATION, THEN I STARTED REALIZING, WELL, YOU KNOW, ALL OF THESE MODELS WOULD BE AN OWN FACE OF NATURAL CLIMATE VARIABILITIES, SO THEY COULD BE SHOWING INCREASES OR DECREASES OVER A PERIOD OF OBSERVATION, BUT THEY ALL SHOW A DECREASE, AND SO THAT'S WHAT STARTS TO HELP IMPLICATE GREENHOUSE GASES THAT'S FORCING THE CHANGES THAT WE'RE SEEING TODAY IN THE ICE COVER.

WE CAN SAY THAT ABOUT 50%-60% OF THE LOSS OF SEA ICE THAT WE'RE SEEING TODAY IS A RESULT OF GREENHOUSE GASES.

THE OTHER 40%-50% IS ACTUALLY NATURAL CLIMATE VARIABILITY, SO WE KNOW BOTH ARE ACTING ON THE SYSTEM RIGHT NOW.

AND RIGHT NOW THE RESULTS ARE ABOUT 50/50, I THINK, ON WHAT'S HAPPENING, WHAT WE'RE SEEING TODAY.

THE PLANET'S GOING TO WARM BY A CERTAIN AMOUNT A DEGREES.

THE SEA ICE IS GOING TO DISAPPEAR IN THE SUMMERTIME.

THE ICE IS CONTINUE TO RESPOND, SEA LEVEL IS GOING TO CONTINUE TO RISE, BUT WHEN WE LOOK AT THINGS LIKE, WELL, WHERE ARE THE PRECIPITATION PATTERNS GOING TO CHANGE?

WHO'S GOING TO GET MORE RAIN?

WHO'S GOING TO GET LESS RAIN?

WHAT'S GOING TO HAPPEN TO THE AMERICAN SOUTHWEST?

ARE THEY GOING TO LOSE THEIR SNOWFALL?

IN THAT SENSE, THERE'S NOT A WHOLE LOT OF ROBUSTNESS BETWEEN THE MODEL SIMULATIONS YET, SO THEY GIVE DIFFERENT ANSWERS IN DIFFERENT REGIONS, AND SO WE DON'T HAVE A GOOD HANDLE, I THINK, ON HOW RAINFALL, FOR EXAMPLE, IS GOING TO CHANGE IN A WARMING CLIMATE.

AND THAT'S REALLY I THINK ONE OF THE KEY THINGS THAT WE NEED TO BETTER UNDERSTAND IS WHERE IS THE WATER GOING TO BE?

BECAUSE A LOT OF REGIONS DEPEND VERY STRONGLY, FOR EXAMPLE, ON THE GLACIER, TO FEED THE CITY AND PROVIDE ALL THE WATER FOR A CITY LIKE SANTIAGO, CHILE, FOR EXAMPLE, AND SO BETTER UNDERSTANDING ON HOW PRECIPITATION IS GOING TO CHANGE AND SNOWFALL IS GOING TO CHANGE IS ONE OF THE KEY THINGS THAT WE NEED TO UNDERSTAND.

WE DO SEE THAT IF YOU RUN POINT-LITIGATION SCENARIOS AND YOU REDUCE THE AMOUNT OF GREENHOUSE GASES, THAT YOU CAN ACTUALLY BRING THE ICE BACK.

YOU CAN STABILIZE THE AMOUNT OF ICE LOSS.

IF WE WERE TO REDUCE OUR GREENHOUSE GASES, IT'S NOT GOING TO BE THIS RUNAWAY EFFECT.

WE CAN STOP SOME OF THESE CHANGES THAT ARE HAPPENING IN THE ARCTIC, BUT THAT DOES MEAN WE'RE GOING TO HAVE TO COMMIT TO REDUCING THE AMOUNT OF FOSSIL FUELS WE'RE PUTTING IN THE ATMOSPHERE, AND THAT'S THE REAL CHALLENGE.

>> MOST EXPERTS SAY FOSSIL FUELS ARE THE LEADING CAUSE OF CLIMATE CHANGE.

THE CLIMATE CHANGE DENIERS OFTEN ASSOCIATED WITH THE FOSSIL FUEL LOBBY AND INDUSTRY-SUPPORTED THINK TANKS DOWNPLAY THE CONNECTION BETWEEN FOSSIL FUELS AND THE WARMING OF OUR PLANET.

CLIMATE SCIENTIST MICHAEL MANN ON HOW A CHANGING CLIMATE MAY AFFECT OUR FUTURE.

>> SOMETIMES YOU'LL HEAR FROM THE CRITICS.

THEY'LL SAY, "WE DEMAND PROOF THAT HUMANS ARE CAUSING THIS."

AND MY RESPONSE IS THAT PROOF IS RESERVED FOR ALCOHOLIC BEVERAGES AND MATHEMATICAL THEOREMS."

IT DOESN'T CHARACTERIZE HOW SCIENCE WORKS.

SCIENCE WORKS THROUGH WEIGHTS OF EVIDENCE, THROUGH LIKELIHOODS, THROUGH CONFIDENCE LEVELS, AND SO WE'RE ABOUT AS CERTAIN THAT HUMANS ARE CAUSING GLOBAL WARMING AS WE ARE ABOUT ANY SCIENTIFIC PROPOSITION, BUT WE NEVER SAY WE'VE PROVEN SOMETHING IN SCIENCE BECAUSE THERE'S ALWAYS THE OUTSIDE CHANCE THAT WE COULD DISCOVER SOME NEW PIECE OF INFORMATION THAT WOULD CHANGE OUR PERSPECTIVE.

IT'S ABSOLUTELY TRUE THAT CRITICS OF SORT OF THE FORCES OF ANTISCIENCE, THOSE LOOKING TO CONFUSE THE PUBLIC ABOUT THE SCIENCE WILL ALWAYS DRAW UPON THAT VULNERABILITY, THAT AS SCIENTISTS WE'RE NEVER COMFORTABLE IN STATING THINGS IN ABSOLUTES BECAUSE THAT'S NOT THE WAY THE WORLD WORKS, THAT'S NOT THE WAY SCIENCE WORKS.

UNFORTUNATELY OUR DETRACTORS, THOSE LOOKING TO SORT OF POLLUTE THE PUBLIC DISCOURSE ON MATTERS OF SCIENCE LIKE GLOBAL WARMING ARE MORE THAN HAPPY TO STATE THEIR OPINIONS WITH ABSOLUTE CERTAINTY.

SO IT'S IMPORTANT TO UNDERSTAND THAT THERE IS SORT OF AN ASYMMETRY IN THE BATTLE OVER INFORMING THE PUBLIC ABOUT SCIENCE.

WE'RE AT A BIT OF A DISADVANTAGE AS SCIENTISTS BECAUSE WE HAVE TO BE TRUE TO OUR PRINCIPLES.

WE HAVE TO BE HONEST.

AND WE HAVE TO RECOGNIZE AND DESCRIBE THINGS IN TERMS OF CAVEATS, IN TERMS OF LAYERS OF UNCERTAINTY.

THERE ARE NO ABSOLUTES.

THAT HAVING BEEN SAID, IT'S PERFECTLY APPROPRIATE FOR A CLIMATE SCIENTIST TO SAY WE ARE NEARLY CERTAIN THAT THE GLOBE IS WARMING BECAUSE OF US, BECAUSE OF INCREASED GREENHOUSE GAS CONCENTRATIONS FROM FOSSIL FUEL BURNING AND OTHER HUMAN ACTIVITIES, AND IF WE CONTINUE ON THE COURSE THAT WE'RE ON, WE ARE LIKELY TO SEE VERY DAMAGING IMPACTS ON US, ON OUR ENVIRONMENT.

ONE OF THE VALID, IN MY VIEW, CRITICISMS OF THE IPCC IS THAT IN MANY RESPECTS IT HAS BEEN OVERLY CONSERVATIVE IN THE WAY IT HAS STATED ITS CONCLUSIONS, AND THERE'S NO BETTER EXAMPLE THAN THE MELTING OF ICE, BOTH SEA ICE, THE LAYERS OF ICE THAT FORM SEASONALLY IN THE ARCTIC, AND AROUND ANTARCTICA, AND LAND ICE, THE MAJOR ICE SHEETS, THE CONTINENTAL ICE SHEETS LIKE THE GREENLAND ICE SHEET AND THE ANTARCTIC ICE SHEET.

IN BOTH RESPECTS, BOTH IN TERMS OF THE SHRINKING AMOUNT OF SEA ICE, FOR EXAMPLE, IN THE ARCTIC AT THE END OF A SUMMER.

THE KIND OF TRAJECTORY THAT WE'RE ON LEADS TO THE CONCLUSION THAT WITHIN A MATTER OF A COUPLE OF DECADES, WE MAY SEE ICE FREE CONDITIONS IN THE ARCTIC AT THE END OF THE SUMMER.

THIS IS SOMETHING THAT THE CLIMATE MODELS PREDICT SHOULDN'T HAPPEN FOR ANOTHER 60 YEARS, 'TIL THE END OF THE 21st CENTURY, AND INDEED NATURE SEEMS TO BE ON A COURSE THAT'S FASTER, THAT'S MORE DRAMATIC THAN WHAT THE CLIMATE MODELS PREDICT.

WE ARE ALREADY OBSERVING AND MEASURING A DECREASE IN THE AMOUNT OF ICE IN THE GREENLAND ICE SHEET AND THE WEST ANTARCTIC ICE SHEET.

NOW, THE CLIMATE MODELS HAVE PREDICTED THAT WE SHOULDN'T SEE THAT FOR MANY DECADES TO COME, AND THE KEY DISTINCTION HERE IS IF IT'S A LAND ICE SHEET, A LAND-BASED ICE SHEET, THEN WHEN IT MELTS, IT ACTUALLY CONTRIBUTES TO GLOBAL SEA LEVEL RISE.

THAT'S NOT THE CASE FOR SEA ICE, BUT IT IS THE CASE FOR THE CONTINENTAL ICE SHEETS, SO THE FACT THAT WE'RE ALREADY MEASURING LOSSES OF ICE FROM THESE MAJOR CONTINENTAL ICE SHEETS MEANS THAT THEY'RE CONTRIBUTING TO SEA LEVEL RISE FASTER, ONCE AGAIN, THAN CLIMATE SCIENTISTS PROJECTED THEM TO.

THERE'S A CREDIBLE BODY OF WORK NOW THAT SUGGESTS THAT IF WE CONTINUE WITH BUSINESS-AS-USUAL FOSSIL FUEL EMISSIONS, THAN BY THE END OF THIS CENTURY, WE COULD SEE AS MUCH AS TWO METERS, 6 FEET OF GLOBAL SEA LEVEL RISE.

NOW, THAT WOULD BE CATASTROPHIC FOR MANY COASTAL REGIONS.

FOR THE U.S. EAST COAST AND GULF COAST, ISLAND NATIONS AROUND THE WORLD, SOME OF WHICH WILL LITERALLY BE SUBMERGED BY THAT AMOUNT OF SEA LEVEL RISE.

THE IPCC MAKES A FAR MORE CONSERVATIVE STATEMENT.

THEY STATE AN UPPER BOUND OF ABOUT A METER, ABOUT 3 FEET, AND IT'S ONCE AGAIN AN EXAMPLE OF WHERE THE IPCC ARGUABLY HAS BEEN OVERLY CONSERVATIVE.

SOME AS MYSELF HAVE ARGUED THAT PARTLY THAT'S JUST DUE TO THE CULTURE OF SCIENCE.

SCIENTISTS TEND TO BE RETICENT.

WE DON'T LIKE TO MAKE STRONG CONCLUSIONS THAT WE HAVE TO WITHDRAW AT SOME LATER TIME.

AND THERE'S ALSO A COMPONENT, I BELIEVE, DUE TO THE PRESSURE, THE OUTSIDE PRESSURE, THE CRITICS, A VERY WELL-FUNDED AND WELL-ORGANIZED EFFORT TO LITERALLY DISCREDIT THE SCIENCE OF CLIMATE CHANGE SOMETIMES BY ATTEMPTING TO DISCREDIT THE SCIENTISTS THEMSELVES.

I MYSELF HAVE BEEN A VICTIM OF THAT.

AND IN THE FACE OF ALL THAT PRESSURE AND THOSE ATTACKS, I THINK TO SOME EXTENT THE IPCC HAS ACTUALLY WITHDRAWN A BIT, AND THEY'VE BEEN MORE GUARDED, MORE CONSERVATIVE, MORE RETICENT IN WHAT THEY'RE WILLING TO CONCLUDE THAN THEY REALLY SHOULD BE GIVEN THE EVIDENCE.

AND ARGUABLY, YOU KNOW, IF IT IS INDEED THE IPCC's ROLE TO ADVISE GOVERNMENTS ON THE POTENTIAL FOR DANGEROUS ANTHROPOGENIC INTERFERENCE WITH THE CLIMATE, WHICH IS WHAT THE IPCC WAS ORIGINALLY CHARGED WITH AS THEIR MISSION, ARGUABLY YOU SHOULD NOT DOWNPLAY THE HIGHER-END SCENARIOS IF THEY'RE CREDIBLE, EVEN IF THEY'RE LOW PROBABILITY OUTCOMES.

IF THEIR PROBABILITY ISN'T ZERO, THEN THEY SHOULD CONTRIBUTE TO THE ASSESSMENT OF RISK MUCH IN THE WAY THAT, YOU KNOW, WE BUY FIRE INSURANCE FOR OUR HOMES NOT BECAUSE WE THINK OUR HOMES ARE GOING TO BURN DOWN.

THAT'S A VERY RARE OCCURRENCE.

IT'S VERY UNLIKELY TO HAPPEN TO US, BUT EVEN THOUGH ITS PROBABILITY IS VERY LOW, THE MAGNITUDE OF COST, THE IMPACT ON OUR LIVES IF OUR HOUSE WAS TO BURN DOWN IS IMMEASURABLE.

MITIGATING CLIMATE CHANGE, DOING SOMETHING ABOUT OUR CARBON EMISSIONS IS A PLANETARY INSURANCE POLICY, AND IN GUIDING THE TERMS OF THAT INSURANCE POLICY, WE NEED TO BE FOCUSING ON SOME OF THOSE POTENTIAL MORE EXTREME CATASTROPHIC OUTCOMES.

IF THE IPCC SYSTEMATICALLY DOWNPLAYS THOSE OUTCOMES, THEN IT DOESN'T SERVE THAT LARGER PROCESS OF SOCIETAL RISK ASSESSMENT AS IT SHOULD.

QUALITATIVELY SPEAKING, IF YOU LOOK AT IMPACTS ON HUMAN HEALTH, WATER AVAILABILITY, HUMAN WATER RESOURCES, FOOD RESOURCES, LAND, THE GLOBAL ECONOMY, PRETTY MUCH EVERY SECTOR OF OUR LIVES, OF HUMAN CIVILIZATION, WHAT YOU SEE IS A BUSINESS-AS-USUAL FOSSIL FUEL BURNING SCENARIO, BY THE END OF THE CENTURY GIVES US HIGHLY NEGATIVE IMPACTS ACROSS THE BOARDS IN ALL THOSE CATEGORIES.

I FORGOT TO MENTION BIODIVERSITY, A POTENTIALLY LARGE-SCALE EXTINCTION OF SPECIES.

SOME OF THESE WE CAN QUANTIFY ECONOMICALLY OR WE CAN TRY TO.

SOME OF THEM WE CAN'T EVEN QUALIFY HOW IMPORTANT THEY ARE.

WHAT IS THE VALUE OF THE EARTH?

WELL, IT'S INFINITE BECAUSE IF WE DESTROY THE EARTH'S ENVIRONMENT, THERE IS NO PLAN "B."

THERE IS NO PLANET "B" THAT WE CAN GO TO.

HOW DO YOU PUT A COST ON, YOU KNOW, ON THE HEALTH OF THE ENVIRONMENT?

ARGUABLY YOU CAN'T EVEN DO SO.

AND IN FACT IT'S THAT PRINCIPLE THAT IT'S AN INFINITE COST WHEN WE START TALKING ABOUT THOSE SORTS OF SCENARIOS THAT LEADS SOME PEOPLE TO, YOU KNOW, CONCLUDE THAT THE PRECAUTIONARY PRINCIPLE APPLIES HERE, THAT THE POTENTIAL IMPACT OF WHAT WE'RE DOING IS SO POTENTIALLY HARMFUL TO US, TO OTHER LIVING THINGS, TO THE PLANET THAT IT'S ALMOST OBVIOUS THAT WE NEED TO MITIGATE THIS PROBLEM, THAT WE NEED TO TAKE ACTIONS NOW TO AVERT THOSE CATASTROPHIC FUTURES, POTENTIAL FUTURES.