Connec&ng(the(Dots(A(Communica&ons(Guide(to(Climate(Change(and(Extreme(Weather(

For(informa&on(contact:

Hunter(Cu=ng(Director(of(Strategic(Communica&ons(Climate(Nexus+1(415D420D7498(hcu=ng@climatenexus.org(

This(work(is(licensed(under(the(Crea&ve(Commons(APribu&onDNoDerivs(3.0(Unported(License.(

New(York,(NY(2012(

Guideline(Summary............................................................................

Introduc&on(and(Overview(................................................................((

Connec&ng(the(Dots...........................................................................((

Examples(of(Effec&ve(Language(........................................................

Signatures(of(Climate(Change............................................................((

Weather(Hallmarks.............................................................................((

How(Do(We(Know?.............................................................................((

What(Not(To(Do(.................................................................................((

Sources(..............................................................................................((

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Table&of&Contents

Paint&the&Big&Picture&First&It# is #important# to#connect#the #dots#by# first#making#the# fundamental # connec8on:# climate # change# is#now#affec8ng#extreme#weather.#

Link&Events&to&Trends&The#signature#of#climate #change#can#be#seen#in#the#weather# trends# driven# by# climate # change.# These#trends # are# the# link# between# individual # weather#events #and#global #warming.# # Connect# the#dots#by#star8ng#with#the#current# event,# explain# how# it# is#consistent# with# the #ongoing# trend,# and# then# link#that#trend#to#climate#change.#

Don’t&Start&Weak&Conversa8ons# in# the #media# are# extremely# short#and#oBen#framed#by#the#first#thing#we#say.#Star8ng#off#by#saying#we #cannot#blame#individual #events #on#climate#change #is #confusing#at#best#and#misleading#at#worst.#Instead,#start#with#what#we#do#know,#and#build#from#there.##

Call&Out&Signature&of&Climate&Change&Talk#about#changes#in#frequency# and#severity.#New#weather# records# and# unprecedented# events # are#also#signals#of#climate#change.#Records#tend#to#be#broken#when# natural #variability# runs# in #the#same#direc8on# as # a # trend# driven# by# global # warming.#Unprecedented# events# can# represent# wild# cards#global#warming#has#added#to#the#climate.#

Learn&the&Hallmarks&The# hallmarks# of# climate # change# are# expressed#differently# in# different# kinds # of# weather# and# in#different# regions.# Learn# the# signatures #of# climate#change#for#your#region.#

Don’t&Debate&the&Consensus&Instead,# compare#climate #change #deniers#to#those#who#disagreed#with#the #consensus #on#smoking#and#cancer# for# many# years# aBer# Surgeon# General’s#warning.#

Don’t&Debate&the&Science&Spending# too#much#8me#rehashing#denier# talking#points #can# reinforce# the # idea # that# the# science# is#controversial.#Instead,#it#is #beKer#to#refer#to#trusted#authori8es#who#have#validated#the#science,#such#as#NOAA,# NASA# and# U.S.# Na8onal # Academy# of#Sciences,#as#well#as #the#insurance#industry#and#U.S.#military.#

Get&the&Language&Right&The# rela8onship# between# extreme# weather# and#climate#change#is #complex.#Learn#the#right#phrasing#to#link#extreme#weather#events #to#climate#change#(see#examples#in#the#sec8ons#below).#

Push&Back&on&QuesEons&Ques8oning# the#link#between#climate #change#and#extreme#weather# is #no# different# than#ques8oning#the#link#between#cancer# and#smoking.# # Make#the#comparison# directly# whenever# the# science # is#ques8oned.#

Don’t&Go&Overboard&With&the&Science&S8ck#to#the#basics.#Focusing#too#much#on#the#niKySgriKy#details #can#detract#from#the#main#points #that#you#want#to#make.

Know&Your&AudienceIntroduce# the # subject# of# climate# change# as#appropriate# for# your# audience.# # Use#messengers#trusted#by#those#who#you#are#trying#to#reach.

Guidelines)Summary

1

IntroducEon&

Extreme(weather( events (are( teachable(moments(on( climate( change.( ( Weather( stories (are (widely(reported( by( the( news( media,( fill ( social ( media(channels,( and( are ( a ( mainstay( of( kitchen( table(conversa&on.( Americans ( are ( par&cularly( good(listeners (when( the(story( is(unfolding( in(their( own(backyards.((

However,( the( dots( between(climate( change ( and( extreme(weather( are(rarely( connected,(and( links(are (o`en( le`( out( of(the( story.( The( connec&ons(between(extreme(weather(and(climate( change( are ( complex(and(can(be(tricky(to(talk(about(in( media ( se=ngs,( where(discussion(is(o`en(reduced(to(sound(bites.( (The(signature(of(climate(change(depends(on(the(kind( of( weather( being( discussed( and( the( region(under( discussion.( In(addi&on,(misinforma&on(and(badDfaith(debate(o`en(cloud(public(conversa&on.((

In( this (se=ng,( helping(Americans(understand(the(link(between(climate(change(and(our( increasingly(severe( weather( requires ( a( wellDcra`ed( and(disciplined(approach.( (What(follows (are(guidelines(for(connec&ng(the(dots.((

Overview&

The( connec&ons ( between( climate( change( and(extreme(weather( are (numerous,( strong( and(wellDdocumented,( and( they( have( been( repeatedly(validated( by( all( of( the ( authorita&ve ( science(ins&tu&ons( dedicated( to( this ( subject,( including(

NASA,2( NOAA3( and( the (U.S.(Na&onal (Academy( of(Sciences.4(

Various( kinds( of( extreme(weather,( such( as (heat(waves ( and( heavy( downpours,( have( increased( in(severity( and(frequency( across (the(globe(in(recent(years,( and( the( increase( is( directly( linked( to( the(changes ( in( the ( climate( driven( by( heatDtrapping(gases ( from( sources ( such( as( smokestacks ( and(tailpipes.5,6,7(

F rom( the ( most( r igorous(perspec&ve,(all(weather(events(are(now( connected(to( climate(change( because( the ( fundDamental ( condi&on( of( the(c l imate( ( the( background(environment( that( gives(rise(to(all(weather)(has(been(altered.8(

Climate ( change( has( both(stacked(the(deck,(making(some(

weather( events (more ( frequent( and( severe,( and(added( wildcards ( to( the ( game,( increasing( the(chances(of(an(occurrence(far(outside(the(norm.9((In(other( words,( climate ( change ( has ( contributed( to(shaPered( records( and( unprecedented( weather(catastrophes.10,11,12(

Individual (events(should(be(viewed(as(part(of(these(larger( trends.( In( the ( case ( of( heat( waves,( for(instance,( that( connec&on( comes( in( the( form( of(more( frequent( and( more( severe( heat( waves.((Extreme(weather( is (driven( by( mul&ple (factors (—(and(global(warming(is(now(one(of(those(factors.13(

IntroducEon&and&Overview

“One% thing% is% certain:%every% weather% event% that%now% happens% is% taking%place% in% the%context%of%our%changing%environment.”&&–(Brady(Phillips,(NOAA1

2

Paint&the&Big&Picture&First&

It( is ( important( to( begin( every( conversa&on,(including( discussions ( about( individual ( weather(events,(by(making(the(fundamental(connec&on:(global ( warming( is ( increasing( many( types( of(extreme(weather.(Much( like (the(Surgeon(General(needed( a ( simple ( statement( to( get( the(message(about( the( risks ( of( smoking( through( to( the(American(public,(speakers(on(climate(change(need(to( lead,( con&nue( and( end( with( the ( simple,(overarching( statement( that( global ( warming( is(already(affec&ng(extreme(weather.(

Talk&About&What&We&Know&

The(media(moves (fast(and(favors (sound(bites (over(substance.( ( O`en,( only( the( very( first( statement(made (will (s&ck( in (the (memory( of( the(reporter( or(the(reader.( (This (se=ng(is (fundamentally( different(from(a(science(classroom.( (Here,(it( is (important(to(start(strong(with(a(statement(about(what(is (known(rather(than(what(is(uncertain.(

Individual (events(can,( in(fact,(be(linked(to(climate(change( through( overarching( trends( in( frequency(and( severity.( Because (climate ( is (the(baseline (for(weather,(altera&on(of(the(climate (correspondingly(affects(all(weather.(

It( is (true(that(one(cannot(“blame”(climate(change(for( any( one(par&cular( weather(event,( just( as(one(cannot( blame( tobacco( for( the( death( of( one(par&cular( smoker.( However,( just( as ( smoking(causes ( cancer,( global ( warming( affects ( extreme(weather.((Climate(change (is (one(of(the(contribu&ng(factors,( along( with( natural ( varia&on( and( other(drivers.( ( And( it( is( important( to( point( out( the(climate( change( link( when( discussing( any( one(par&cular(event.(

Link&Events&to&Trends&

The( signature( of( climate ( change( can( be( seen( in(weather( trends.( ( These( trends( have( very( clear(characteris&cs,( and( they( are ( the ( link( between(individual ( weather( events ( and( global ( warming.((Connect( the( dots ( by( star&ng( with( the( current(weather,( explain( how( it( is( consistent( with( the(ongoing( trend,( and( then(link( that( trend(to(global(warming.((

Unusually( severe( or( frequent( events( may( offer(examples (of( the(trends(driven(by( climate (change.(For(example,(heat(waves (are(becoming(both(more(frequent(and(severe.((When(a (recordDbreaking(heat(wave ( sweeps( over( your( city,( that( event( is(consistent(with(the (longDterm(climate (change(trend(toward(more(severe(heat(waves.( (That( is(a (link(to(global (warming(that(can(and(should(be(made.(New(weather(records (and(unprecedented(events (can(be(par&cularly( strong( indicators (of( climate(change.14((Records(tend(to(be (broken(when(natural (variability(runs (in (the(same(direc&on(as (the (trend(driven(by(global(warming.(

Climate(change(has(different(hallmarks (in(different(kinds ( of( extreme( weather.( Work( with( local(scien&sts (to( understand(the(signatures(of( climate(change(for(the(weather(in(your(region.((See(Climate(Change(Signatures(and(Weather(Hallmarks (on(pgs.(7(and(8(for(more (informa&on(about(different(kinds(of(extreme(weather( such(as(heat(waves,(drought,(floods(and(rainstorms.(

ConnecEng&the&Dots

3

Use&the&Right&Language&

Because( many( factors ( drive( extreme( weather,(including(climate(change,( it( is (helpful (to(learn(and(use(the(right( language(for(connec&ng(the (dots(for(different(kinds(of(weather.(

Know&the&Changes&for&Your&Region&

Some(of(the(trends (in(extreme(weather( driven(by(climate( change( are ( global ( while( other( trends,(par&cularly( those( trends(related(to(precipita&on,(vary(significantly( by( region.( The(science(on(extreme(weather(and( cl imate( change( is(rapidly( coming( into( focus,(and( more ( links ( are( found(almost(every(month.((

For( example,( the( recordDbreaking( “once( in( one(thousand( years”( rain( that(caused(the(historic(floods (in(Nashville( in( May( 2010( is(part(of( the(longDterm(global(trend( of( precipita&on( shi`Ding( toward( heavier( events.(Research(has (fully(documented(and(aPributed(this(trend( to( climate ( change.( Moreover,( the( southDcentral ( U.S.( in( par&cular( has ( experienced(increasingly( heavy( spring&me( precipita&on( in(recent( years.15( One( can( and( should( say( the(Nashville(flood(is (linked(to(climate(change(by(virtue(of(fi=ng(the(longDterm(trend(in (heavy( rain(driven(by(global(warming.((

It( is (important( to(know(the(science (and(trends(for(your( area.( One( recent( authorita&ve ( source( is("Global ( Climate( Change ( Impacts ( in( the ( United(States",( a( science( report( commissioned( and(produced( by( the( federal ( government( under(President( George(W.( Bush,( and( released( by( the(Obama (Administra&on.(The(report(details (weather(impacts( in( the (United( States (by( region.( Another(helpful( science( primer( is ( "Climate ( Change( and(

Recent( Extreme( Weather",( published( by( Climate(Communica&on.( ( Also(see(the("Special (Report( on(Extremes"( published( by( the( Intergovernmental(Panel(on(Climate(Change.((

Acknowledge&Natural&VariaEon&

While(global (warming(is (now(a (contribu&ng( factor(to(all(weather( events,(natural (varia&on(has (always(been( and( will ( con&nue( to( be( a (major( factor( in(determining(dayDtoDday(weather.((It(is (important(to(

lead( conversa&ons ( about(extreme(weather( events (by(spotligh&ng( and( explaining(their( connec&on( to( global(warming.( ( As ( the( converDsa&on( deepens( and( gains(nuance,( it( can( be( approDpriate( at( &mes( to( ackDnowledge(the(role (of(natural(v a r i a&on .( ( Howeve r ,(remember(the (goal (is (not(to(deliver( a(science(lesson,( but(r a the r( to( an swer( the(ques&on( that( Americans(want( to( know:( is( extreme(weather( related( to( global(warming?(

Push&Back&When&Link&is&QuesEoned

Ques&oning( the (link(between(climate(change(and(extreme(weather( is(no(different( than(ques&oning(the( link( between( smoking( and(cancer( or( the(link(between(HIV(and(AIDS.( (Those(comparisons(should(be ( made( directly( whenever( the ( science( is(ques&oned.(

“When%we%see%records%being%broken%and% unprecedented% events% such% as%this,%the%onus%is%on% those%who%deny%any%connec@on%to%climate%change%to%prove% their% case.% Global% warming%has% fundamentally% altered% the%background%condi@ons%that%give%rise%to%all%weather.%In%the%strictest%sense,%all% weather% is% now% connected% to%climate%change.”–"Dr."Kevin"Trenberth37

4

It(is (important(to(dis&nguish(whether(the(ques&ons(are(born(of(honest( ignorance(or(badDfaith(debate.(But( in( either( case( it( is ( important( to( defend( the(facts (and(assert(that(the(science(is (strong.(The(only(ques&on(now(is(what(we(do(about(it.(

However,( do( NOT( get( into( a( debate ( about( the(science.( Instead,( simply( point( out( that( the(most(trusted(authori&es,(NOAA,(NASA(and(U.S.(Na&onal(Academy( of( Sciences,( have( all( found( the ( same(connec&ons.( ( In(addi&on,(the(U.S.(military(and(the(insurance( industry( have( validated( the( science.( If(those( authori&es( are ( not( good( enough( for( your(listeners,(then(the (conversa&on(is (probably(a (waste(of(&me.(

Challenge&Alternate&ExplanaEons&

Some&mes ( El( Niño,( blocking( events ( and( other(circula&on( changes( are ( cited( as( the( cause( of(unprecedented( or( recordDbreaking( extreme(weather.( However( these( kinds (of( “explana&ons”(do(not( iden&fy( the (ul&mate(drivers (of( the (event,(among(which( climate( change(should( be(counted.(APribu&ng( an( extraordinary( and( unpredictable(extreme(weather( event( to(a (circula&on(change(is(like( saying( the ( engine( was( responsible( for(accelera&ng( the(car.( ( The(real (ques&on( remains:(where( did( the( extra ( fuel ( come( from?( One(contribu&ng(factor(is(climate(change.16(

5

•(Global(warming(is(helping&to&fuel(this(heat(wave.(

• This (deluge( is (consistent& with& the& recent& trend&toward( more( heavy( rainfall,( a ( trend( driven( by(global (warming( that( loads (more( moisture( into(the(atmosphere.

• This (category( 5( hurricane( is (an& example& of& the&

stronger& hurricanes& we& can& expect& to& see( as(global (warming( intensifies (due(to(heatDtrapping(gases ( f rom( smokestacks ( and( ta i lp ipes(accumula&ng(over(the(coming(years.(

• Global (warming(is (contribuEng&to( this (drought(by(driving(up(temperatures,(which(in(turn(dries (out(soil.

• The( shi`( in( rain( from(moderate(to(heavier( but(less( frequent( downpours (means(greater( runDoff(and( less ( water( absorbed( by( soils.( ( This((contributes&to(drought.

• Climate( change( is (making( heat( waves ( like& the&one&we&are&experiencing&now(more(frequent.

• Due (to( climate(change,(we’ve& set& the& table( for(this(kind(of(extreme(weather.

• Global (warming(has (stacked& the&deck(with(extra(aces,(making(events(like(this(more(severe

• Climate( change ( has ( loaded& the& dice,( making(events(like(this(more(frequent.

• Global (warming(is (the(climate&on&steroids.(Like(a(ball (player( on(steroids (hi=ng(more(home(runs,(heatDtrapping( gases ( from( smokestacks ( and(tailpipes (are (fueling(more(extreme(weather( like(this.

• This (heat(wave (is (one& event& in& the& larger& trend(toward( longer,( hoPer( and( more( frequent( heat(waves,( a ( trend( driven( in( large ( part( by( global(warming.

• Unprecedented(events (like(this (super( swarm(of(tornadoes( could& represent& the& wildcards( that(global(warming(has(introduced(into(the(climate.

Examples&of&EffecEve&Language

6

Ongoing(trends(in(extreme(weather(bear( the (clear(signature (of(climate (change,(and(they( are(the (link(between( individual( weather( events ( and( climate(change.((

Changes&in&Frequency&

Global ( warming( has ( increased( the( frequency( of(many(events (such(as (heat(waves(and(heavy( rains,(and(decreased(the(frequency(of(other(events(such(as (cold( snaps.( ( Records(tend(to(be(broken(when(natural(variability(runs (in (the(same(direc&on(as (the(trend( driven( by( global(warming.17( ( For( example,(when( a ( region( begins( experiencing( heat( waves(more( frequently( than( historical( averages,( it( is(important( to(point( out( the( growing( global ( trend(toward(more(frequent(heat(waves.

Changes&in&Severity&

Warming(has(increased(the (severity(of(events (such(heat(waves(and(heavy(rains.( (When(these(kinds (of(extreme(events (are (more (severe(than(average,(it(is(an(opportunity(to(point(out(that(climate(change(is(driving(the(trend(towards(more(severe(events.(

For( some ( kinds( of( extremes,( such( as ( recordDbreaking( heat( waves,( the( direct( connec&on( to(global ( warming( can( be ( found( in( almost( every(event.( ( Not(only( has (global(warming( changed(the(fundamental (condi&on(of(the(climate,(but(warming(is ( also( a( direct( contribu&ng( factor( to( local(temperatures,( including( heat( waves.( ( The(background( condi&on( for( heat( waves ( is ( now( a(couple ( of( degrees ( hoPer.( In( this ( way,( global(warming( contributes ( directly( to( the( severity( of(individual ( heat( waves( and( can( make( them( last(longer.( (Drought,( too,( can(be (directly( affected,( as(dry( condi&ons ( are( o`en( driven( by( hot( tempDeratures(that(dry(out(the(ground.(

New&Records&

Global (warming(has (changed(the(natural (limits (and(greatly( increased( the( severity( of( certain( kinds(of(extreme(weather.( (As(a (result(we(are(witnessing(a(change(in(the(paPern(of(record(weather(observed(each(year.((New(records (for(temperature (highs,(24Dhour(rainfall (totals (and(the(like(are(consistent(with(the(trends (driven(by(global (warming.( (We(can(and(should( point( this ( out( when( discussing( individual(extreme(events.(Without(climate(change(we (would(s&ll (see(new( weather( records(set( each( year,( due(simply( to( natural (varia&on.( ( However,( we(would(expect(see(as (many( new(records(for(cold(weather(as (we(would(for(hot(weather.((Over(&me,(we(would(expect(the(number(of(new(records (set(each(year(to(decline(as(the(law(of(averages (takes(over.( ( Instead(we ( are( witnessing( a( drama&c( increase( in( the(number(of(new(record(highs (set(each(year(at((more(weather(sta&ons(across(the(United(States.

Unprecedented&Events&

Global ( warming( has( changed( the( fundamental(condi&on( of( the( climate,( and( as ( noted( above,(changed( the ( natural ( limits.( ( A( small ( change( in(global (temperature (makes(for(a (drama&c(change(in(extreme( weather.18( Indeed,( the( average( global(temperature(during( the(last( ice (age(was(only( 9°( F(colder(than(recent(preDindustrial (levels.(As(a(result,(unprecedented( weather( events ( could( represent(the( wildcards( climate( change( has( added( to( the(deck.19( These (events (are( an(opportunity( to( point(out(the(new(cards(in(play.(

Signatures&of&Climate&Change

7

Weather&Hallmarks

The( hallmarks ( of( climate( change( are ( expressed(differently(in(different(kinds (of(weather,(and(each(is(worth( no&ng( when( extreme( weather( arrives(bearing( these( par&cularly( dis&nc&ve( charDacteris&cs.(

Heat&waves&

For( heat( waves,( the( signal( of( climate( change( is(par&cularly( strong( in (the(trend( toward(hot( nights((i.e.(elevated(overnight(low(temperatures)(and(high(humidity.( ( However,( the (signal(of( climate(change(has (been(documented(in(the(current(trend(toward(hoPer(days(as(well.20(

Rain(

While(total(global (precipita&on(has(remained(flat(or(increased(slightly,(climate (change(has (drama&cally(reworked(the(paPern(of(wet(and(dry(areas(around(the( world.( ( The( global( sub¬tropical ( belt,( which(includes( U.S.( Southwest,( is( drying( out,( while( the(midDla&tude(belt,(which(includes (the(U.S.(Midwest,(is(seeing(significant(increases(in(rain(and(snow.21(

Importantly,(precipita&on(is(increasingly( becoming(concentrated(into(heavy(downpours(spaced(further(apart,(and(the(role (of(climate(change(in(driving(this(global ( trend( has ( been( established.( Even( areas(seeing( less ( precipita&on( overall ( are ( experiencing(this(trend(toward(concentrated(downpours.22(

Snow(

Heavier( snowfalls ( are ( consistent( with( climate(change.( A(warmer( atmosphere (holds (more(water,(which(will (con&nue (to(fall (as(snow(as(long(as (winter(temperatures(don’t(rise(above (freezing.23( (The(U.S.(Northeast,( for( example,( has( seen( an( extremely(

drama&c( increase( in( oneDday( precipita&on(extremes(during(the(Oct.DMarch(cold(season.24((

Tornadoes(

There( is ( no( clear( longDterm( trend( in ( tornadoes.((However( the( recent,( unprecedented( tornado(outbreaks(in(the (United(States (could(represent(the(wild( cards ( that( have( been( introduced( into( the(climate( by( global( warming.34( Computer( models(indicate( that( condi&ons ( favorable( to( tornadoes(may(increase(in(some(regions.35(

Flooding(

Flooding,( like( drought,( is ( par&cularly( tricky( to(discuss ( as( it( can( be( driven( by( factors ( such( as(development,( levee( placement( and( local(topography.( ( That( said,( look( for( unusually( heavy(rains,( early( snowmelt,( or( record( seasonal(precipita&on( as( contribu&ng( factors ( that( are(affected(by(climate(change.28(

Storms(

Climate(change(is(driving(up(the(intensity(of(storms(by( providing( them(with(more (energy.( ( All(storms,(including( thunderstorms,( extra( tropical ( rain,(snowstorms( and( tropical ( cyclones( are( now(developing( in( a( warmer( and( more( moist(environment.29( ( General( storminess ( around( the(world,( as (measured( by( winds( speeds ( and( ocean(wave(heights,( has (increased( in( recent( years,(with(the( increase( par&cularly( pronounced( in( winter(months.30

8

Hurricanes(

For( hurricanes,( focus( on( the ( intensity( of( storms,(not( their( frequency.( ( It( is ( par&cularly( useful ( to(highlight( the( role( global ( warming( has ( played( in(increasing( the(heavy( rain( carried(by( storms.( ( For(many( storms,( the(damages (are(wrought( as(much(by( heavy( rains(and(the (followDon(flooding(as (from(wind( damage( and( storm( surge.( Hurricanes ( that(dump( recordDbreaking( amounts( of( precipita&on(are( consistent( with( the( trend( driven( by( climate(change(toward(heavy(rainstorms.31(

The( recent( trend( has ( been( toward( stronger(hurricanes.( While ( there ( is ( some( debate ( over(whether( to(aPribute(this (trend(to(climate (change(or( natural (varia&on,( there( is( a (consensus (among(the(experts (that( in(the (future(global(warming(will(result(in(stronger(hurricanes.32((

Although( the ( Atlan&c( basin( is ( poised( to( see ( a(drama&c( increase( in( the( number( of( very( strong(hurricanes,( the(global (tropical (cyclone(count(may(decline(slightly.33(Unfortunately,( these(two(trends(may( not( balance( out,( as ( the (damage( caused( by(stronger( hurricanes (is( exponen&ally( greater( than(the(damage(wrought(by(lesser(storms.(There(is (also(the ( prospect( for( bigger( hurricanes,( but( this(possibility(has(not(been(well(explored.((

As ( such,( one ( can( say( that( par&cularly( strong(hurricanes (are( an( example( of( what( will( become(much( more( common( in( future( years( as ( global(warming(becomes (locked(in(due(to(heatD(trapping(gases (from(smokestacks (and(tailpipes(accumula&ng(in(the(atmosphere.(((

Finally,( hurricane( storm( surge ( now( rides ( higher(upon( seas (that( have( risen( over( the( last( century,(much(of(which(is (aPributable(to(mel&ng(ice(sheets(and( a(warmer,( expanding( ocean.( ( The( rising( sea(level (gives (storm(surge(a (higher( point( for( jumping(off(onto(land.((

Drought

There(has (been( an( increase (in(drier,( hoPer( areas(around( the ( world,( and( dry( areas ( are ( becoming(drier,( par&cularly( in( the( subtropical (band( circling(the(globe,(a (band(that(includes(Texas,(New(Mexico(and(Arizona.( (The (global (trend(is (directly( linked(to(warming(of(the(atmosphere.25(

How&Do&We&Know?

There(are(several (ways (we(know(climate(change(is(affec&ng(extreme(weather.(

Basic( physical (principles (offer( the( first(proof.( ( For( example,( we (know( that( a(warmer( atmosphere ( holds (more ( heat(and( more( energy.( ( As ( a ( result,( the(hoPest( days ( are( even( hoPer.( Or,( in(another( example,( we( know( that( a(warmer( atmosphere( can( hold( more(moisture,( so( the( heaviest( rainstorms(now(dump(more(water(than(before.(

The( second( line ( of( proof( is ( by( direct(scien&fic(measurement.(Many( different(kinds ( of( extreme ( weather( have(drama&cally( changed( over( the( last(several ( decades.( These( trends ( have(been(rigorously(measured,(and(they(go(well(beyond(natural(variability.(

The(computer(models (that(simulate(the(climate( offer( the( third( line( of( proof.((These( models ( can( only( replicate ( the(current( trends( in( extreme ( weather(when( addi&onal( greenhouse( gases(are(added( to( the ( their( inputs.( Natural(variability( in( the( models( alone ( can’t(produce (the(trends (we(observe (in( the(real(world.

9

Moreover,( areas ( around( the ( world( are( seeing(increasingly( wide( swings ( between( wet( and( dry(extremes,(another(hallmark(of(climate(change(due(to(global(warming.( (A(warmer(climate,(like(a(larger(bucket,( can( hold( and( dump( more( water,( but( it(takes(longer(to(refill.26(

For( drought,( early( snowmelt( and(record(heat( are(contribu&ng( factors( that( are( par&cularly(characteris&c(of(climate(change.((Depending(on(the(regional ( precipita&on( trend( driven( by( climate(change,(shorwalls (in(precipita&on(in(any(one(region(may(be(consistent(with(global(warming.27(

Dock(and(dry(reservoir(at(Copper(Breaks(State(Park,(Texas.((Fall(2011.

10

Don’t&Debate&the&Science&&

Instead,( point( out( that( the ( most( trusted(authori&es,( NOAA,( NASA( and( U.S.( Na&onal(Academy(of(Sciences(have(all (judged(and(validated(the(science,(as(has (the(insurance(industry( and(the(U.S.(military.(

Don’t&Debate&the&Consensus&&

Instead,( explain( climate( change( deniers( by(comparing( them(to(those(who(disagreed(with(the(consensus (on(smoking( and(cancer( for( many( years(a`er(Surgeon(General’s (warning.((It(is (also(useful (to(point(out( that(most(of(the(prominent( skep&cs (are(funded(by( the(oil (industry.( (If(you(wouldn’t(bet(the(farm(on(the(sayDso(of(the(handful (of(scien&sts (who(believe(in(UFOs,(why( should(we(put(our(children’s(future(at(risk(on(the(sayDso(of(a(handful(of(climate(change(deniers?(

Avoid&Blanket&Statements

Avoid( statements ( such( as ( “climate( change( is(increasing(extreme(weather,”(as(that(is (not(strictly(correct.( ( Some ( kinds( of( extreme( weather,( cold(snaps ( for( instance,( are( decreasing.( ( Instead,( say(“climate ( change( is ( increasing( some( kinds( of(extreme(weather.”

Don't&Give&a&Technical&Lecture

Americans (are(not(looking(for(a(science(lesson,(and(science( arguments ( alone( tend( not( to( be( very(persuasive( with( Americans.36( ( Americans ( simply(want( to( know( if( there( is ( a( connec&on( between(extreme( weather( and( climate ( change.( We( can(address( that( interest( to( help( people( understand(the( risks ( in( overloading( the( atmosphere( with(carbon(pollu&on,(as(well(as(the(choices(we(have.(

Don't&Start&Weak

Do( not( lead( by( telling( people( that( you( cannot(aPribute( any( single( event( to( climate( change,( or(that(you(can’t(blame(global(warming(for(individual(events.( (Instead,(start(with(what(we(do(know,(and(go(from(there.(

Acknowledgements:( ( Thanks ( to( Susan( Hassol,(Aaron( Huertas,( Michael( Mann,( and( Kevin(Trenberth,(who(provided(invaluable(comments (on(early( versions( of( this (document.( ( Any( wayward(passages (in(this (final (document(belong,(of(course,(to(the(author(alone.(

For(more(informa&on(contact:(Hunter(Cu=ng(Director(of(Strategic(Communica&ons(Climate(Nexus(+1(415D420D7498hcu=ng@climatenexus.org(

11

1. Winter(forecast(offers(no(hope(for(Texas,(The(Daily(Climate,(Nov.(17,(20011.(hPp://wwwp.dailyclimate.org/tdcDnewsroom/2011/11/winterDweather

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3. Gutowski,(W.J.,(G.C.(Hegerl,(G.J.(Holland,(T.R.(Knut¬son,(L.O.(Mearns,(R.J.(Stouffer,(P.J.(Webster,(M.F.(Wehner,(F.W.(Zwiers,(2008:(Causes(of(Observed(Changes(in(Ex¬tremes(and(Projec&ons(of(Future(Changes(in(Weather(and(Climate(Extremes(in(a(Changing(Climate.(Regions (of(Focus:(North(America,(Hawaii,(Caribbean,(and(U.S.(Pacific(Islands.(T.R.(Karl,(G.A.(Meehl,(C.D.(Miller,(S.J.(Hassol,(A.M.(Waple,(and(W.L.(Murray((eds.).(A(Report(by(the(U.S.(Climate(Change(Science(Program(and(the(SubcommiPee(on(Global(Change(Research,(Washington,(DC.((hPp://www.climate¬science.gov/Library/sap/sap3D3/finalDreport/default.htm(

4. Panel(on(Advancing(the(Science(of(Climate(Change;(US(Na&onal(Research(Council((2010).(“Summary”.(Advancing(the(Science(of(Climate(Change.(Na&onal(Academy(Press,(Washington,(D.C.,(USA.(p.(3.(ISBN(978D0D309D14588¬6(hPp://dels.nas.edu/Report/AdvancingDScienceDClimate¬Change/12782(

5. StoP,(P.(A.,(GilleP,(N.(P.,(Hegerl,(G.(C.,(Karoly,(D.(J.,(Stone,(D.(A.,(Zhang,(X.(and(Zwiers,(F.(,(2010:(Detec&on(and(aPribu&on(of(climate(change:(a(regional(perspec&ve.(Wiley(Interdisciplinary(Reviews:(Climate(Change,(1:(192–211.(doi:(10.1002/wcc.34

6. Chris&dis,(N.,(P.A.(StoP,(and(S.(Brown,(2011:(The(role(of(human(ac&vity(in(the(recent(warming(of(extremely(warm(day&me(temperatures.(Journal(of(Climate(doi:10.1175/2011JCLI4150.1(hPp://

journals.ametsoc.org/doi/abs/10.1175/2011JCLI4150.1(

7. Min(S.,(X.(Zhang,(F.(Zwiers,(and(G.(Hegerl,(2011:(Human(contribu&on(to(moreDintense(precipita&on(extremes.(Nature(2011(Volume:(470,(Pages:(378–381.(doi:10.1038/nature09763

8. Trenberth,(K.E.(2011:(APribu&on(of(climate(varia&ons(and(trends(to(human(influences(and(natural(variability.(Wiley(Interdisciplinary(Reviews:(Climate(Change,(in(press.(

9. Gutowski,(W.J.,(G.C.(Hegerl,(G.J.(Holland,(T.R.(Knut¬son,(L.O.(Mearns,(R.J.(Stouffer,(P.J.(Webster,(M.F.(Wehner,(F.W.(Zwiers,(2008:(Causes(of(Observed(Changes(in(Ex¬tremes(and(Projec&ons(of(Future(Changes(in(Weather(and(Climate(Extremes(in(a(Changing(Climate.(Regions (of(Focus:(North(America,(Hawaii,(Caribbean,(and(U.S.(Pacific(Islands.(T.R.(Karl,(G.A.(Meehl,(C.D.(Miller,(S.J.(Hassol,(A.M.(Waple,(and(W.L.(Murray((eds.).(A(Report(by(the(U.S.(Climate(Change(Science(Program(and(the(SubcommiPee(on(Global(Change(Research,(Washington,(DC.((hPp://www.climate¬science.gov/Library/sap/sap3D3/finalDreport/default.htm(

10. Hoerling,(M.,(J.(Eischeid,(X.(Quan,(and(T.(Xu,(2007:(Explaining(the(record(2006(US(warmth.(Geophys.(Res.(LePers,(34,(doi:10.1029/2007GL030643.(hPp://www.publicaffairs.noaa.gov/releases2007/aug07/noaa07D045.html

11. Wergen,(G.(and(J.(Krug,(2010:(RecordDbreaking(temperatures(reveal(a(warming(climate.(Europhysics(LePers,(Volume(92,(Issue(3,(pp.(30008((2010).(DOI:(10.1209/0295D5075/92/30008

12. Trenberth,(K.E.(2011:(APribu&on(of(climate(varia&ons(and(trends(to(human(influences(and(

12

natural(variability.(Wiley(Interdisciplinary(Reviews:(Climate(Change,(in(press.

13. Karl,(T.R.,(J.M.(Melillo,(and(T.C.(Peterson,(2009:(Global(Climate(Change(Impacts(in(the(United(States.(Cambridge(University(Press,(2009.(

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15. Karl,(T.R.,(J.M.(Melillo,(and(T.C.(Peterson,(2009:(Global(Climate(Change(Impacts(in(the(United(States.(Cambridge(University(Press,(2009.(

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17. Ibid.(

18. Peterson(et(al.(2008:(Why(Weather(and(Climate (Extremes(MaPer(in(Weather(and(Climate(Extremes(in(a(Changing(Climate.(Regions(of(Focus:(North(America,(Hawaii,(Caribbean,(and(U.S.(Pacific(Islands.(T.R.(Karl,(G.A.(Meehl,(C.D.(Miller,(S.J.(Hassol,(A.M.(Waple,(and(W.L.(Murray((eds.).(A(Report(by(the(U.S.(Climate(Change(Science(Program(and(the(SubcommiPee(on(Global(Change(Research,(Washington,(DC.((hPp://www.climatescience.(gov/Library/sap/sap3D3/finalDreport/default.htm(

19. Trenberth,(K.(E.,(2011:(Changes(in(precipita&on(with(climate(change.(Climate(Research.(doi:10.3354/cr00953,(in(press.(

20. Chris&dis,(N.,(P.A.(StoP,(and(S.(Brown,(2011:(The(role(of(human(ac&vity(in(the(recent(warming(of(extremely(warm(day&me(temperatures.(Journal(of(Climate(doi:10.1175/2011JCLI4150.1hPp://journals.ametsoc.org/doi/abs/10.1175/2011JCLI4150.(See(also(IPCC,(2011:(Summary(for(Policy(Makers.(In:(Special(Report(on(Extremes.(hPp://ipccDwg2.gov/SREX/(

21. Trenberth,(K.(E.,(2011:(Changes(in(precipita&on(with(climate(change.(Climate(Research.(doi:10.3354/cr00953,(in(press.(

22. Min(S.,(X.(Zhang,(F.(Zwiers,(and(G.(Hegerl,(2011:(Human(contribu&on(to(moreDintense(precipita&on(extremes.(Nature(2011(Volume:(470,(Pages:(378–381.(doi:10.1038/nature09763.((See(also(Trenberth,(K.E.(2011:(APribu&on(of(climate(varia&ons(and(trends(to(human(influences(and(natural(variability.(Wiley(Interdisciplinary(Reviews:(Climate(Change,(in(press.(

23. Trenberth,(K.(E.,(2011:(Changes(in(precipita&on(with(climate(change.(Climate(Research.(doi:10.3354/cr00953,(in(press.(

24. NOAA(Satellite(and(Informa&on(Service.(hPp://www.(ncdc.noaa.gov/extremes/cei/graph/ne/4/10D03(

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28. IPCC,(2011:(Summary(for(Policy(Makers.(In:(Special(Report(on(Extremes.(hPp://ipccDwg2.gov/SREX/(

29. Trenberth,(K.(E.,(2011:(Changes(in(precipita&on(with(climate(change.(Climate(Research.(doi:10.3354/cr00953,(in(press.(

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13

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35. Trapp,(R.J.,(N.S.(Diffenbaugh,(H.E.(Brooks,(M.E.(Baldwin,(E.D.(Robinson,(and(J.S.(Pal,(2007:(Severe(thunderstorm(environment(frequency(during(the(21st(century(caused(by(anthropogenically(enhanced(global(radia&ve(forcing,(PNAS(104(no.(50,(19719D19723,(Dec.(11,(2007.(

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