Global warming of 1.5ᵒC Frequently Asked Questions

Global warming of 1.5ᵒC Frequently Asked Questions First Lead Author Meeting São José dos Campos, Brazil 6-10 March 2017

Purpose of Frequently Asked Questions To provide information on issues of broad interest at the level of the informed adult public, understandable to non-technical readers Intended audience: policymakers, advisors, teachers, students, media, public FAQs are part of the chapters they are drafted and owned by the Lead Author(s), and reviewed with the rest of the chapter FAQs will be edited by professional science writer, but in close liaison with LAs but LAs have overall responsibility at all times FAQs also need to be stand-alone (possibly to be compiled in a separate volume) FAQs are topically embedded in the appropriate chapter but the set of FAQs across the chapters ideally form a coherent storyline

Example: WGI AR5 FAQ 2.1: How Do We Know the World Has Warmed? Frequent ly Asked Quest ions Frequent ly Asked Quest ions FAQ 2.1 How Do W e Know the World Has Warmed? Evidence f or a w arming w orld comes f rom mult iple independent climat e indicat ors, f rom high up in t he at mosphere t o t he dept hs of t he oceans. They include changes in surf ace, at mospheric and oceanic t emperat ures; glaciers; snow cover; sea ice; sea level and at mospheric w at er vapour. Scient ist s f rom all over t he w orld have independent ly veriﬁ ed t his evidence many t imes. That t he w orld has w armed since t he 19t h cent ury is unequivocal. Discussion about climat e w arming of t en cent res on pot ent ial residual biases in t emperat ure records f rom landbased w eat her st at ions. These records are very import ant, but t hey only represent one indicat or of changes in t he climat e syst em. Broader evidence f or a w arming w orld comes f rom a w ide range of independent physically consist ent measurement s of many ot her, st rongly int erlinked, element s of t he climat e syst em (F AQ 2.1, Figure 1). A rise in global average surf ace t emperat ures is t he best -know n indicat or of climat e change. Alt hough each year and even decade is not alw ays w armer t han t he last, global surf ace t emperat ures have w armed subst ant ially since 1900. Warming land t emperat ures correspond closely w it h t he observed w arming t rend over t he oceans. Warming oceanic air t emperat ures, measured f rom aboard ships, and t emperat ures of t he sea surf ace it self also coincide, as borne out by many independent analyses. The at mosphere and ocean are bot h ﬂ uid bodies, so w arming at t he surf ace should also be seen in t he low er at mosphere, and deeper dow n int o t he upper oceans, and observat ions conﬁ rm t hat t his is indeed t he case. Analyses of measurement s made by w eat her balloon radiosondes and sat ellit es consist ent ly show w arming of t he t roposphere, t he act ive w eat her layer of t he at mosphere. M ore t han 90% of t he excess energy absorbed by t he climat e syst em since at least t he 1970s has been st ored in t he oceans as can be seen f rom global records of ocean heat cont ent going back t o t he 1950s. (continued on next page) Glacier Volume Air Temperature in the lowest few Km (troposphere) Water Vapor Temperature Over Land Sea Ice Area Snow Cover Marine Air Temperature Sea Surface Temperature Sea Level Ocean Heat Content FAQ 2.1, Figure 1 Independent analyses of many components of the climate system that would be expected to change in a warming world exhibit trends consistent with warming (arrow direction denotes the sign of the change), as shown in FAQ 2.1, Figure 2. FAQ

FAQ 2.1 How Do W e Know the World Has Warmed? Evidence f or a w arming w orld comes f rom mult iple independent climat e indicat ors, f rom high up in t he at mosphere t o t he dept hs of t he oceans. They include changes in surf ace, at mospheric and oceanic t emperat ures; glaciers; snow cover; sea ice; sea level and at mospheric w at er vapour. Scient ist s f rom all over t he w orld have independent ly veriﬁ ed t his evidence many t imes. That t he w orld has w armed since t he 19t h cent ury is unequivocal. FAQ Consistent Structure: Question, summary reply in italics, supporting text with supporting graphic(s), conclusion Frequent FrequentlylyAsked AskedQuest Questions ions Discussion about climat e w arming of t en cent res on pot ent ial residual biases in t emperat ure records f rom landbased w eat her st at ions. These records are very import ant, but t hey only represent one indicat or of changes in t he climat e syst em. Broader evidence f or a w arming w orld comes f rom a w ide range of independent physically consist ent measurement s of many ot her, st rongly int erlinked, element s of t he climat e syst em (F AQ 2.1, Figure 1). A rise in global average surf ace t emperat ures is t he best -know n indicat or of climat e change. Alt hough each year and even decade is not alw ly aysasked w armer tquest han t heions last, global surf ace t emperat ures have w armed subst ant ially since 1900. Frequent Frequently Asked Questions FAQ FAQ2.1 2.1 How HowDo DoW WeeKnow Knowthe theworld WorldHas HasWarmed? Warmed? Warming land t emperat ures correspond closely w it h t he observed w arming t rend over t he oceans. Warming oceanic air t emperat ures, measured f rom aboard ships, and t emperat ures of t he sea surf ace it self also coincide, as borne out by many independent analyses. The at mosphere and ocean are bot h ﬂ uid bodies, so w arming at t he surf ace should also be seen in t he low er at moevidence world comes independent climate indicators, sphere, and deeper dow for n int oat he upper oceans, and observat ions from conﬁ rm multiple t his is indeed t he case. Analyses of Evidence for awarming warming world comes fromt hat multiple independent climate indicators,from fromhigh highup upininthe theatmosphere atmosphere measurement s made by w eat her balloon radiosondes and sat ellit es consist ent ly show w arming of t he t roposphere, to the depths of the oceans. They include changes in surface, atmospheric and oceanic temperatures; t he act ive wto eat her of t he atof mosphere. M ore t hanthey 90% ofinclude t he excess energy absorbed t he climat atmospheric e syst em thelayer depths the oceans. changes in by surface, and oceanic temperatures;glaciers; glaciers;snow snow since at least t he 1970s has beensea st ored in t heand oceans as can be seen f rom global vapour. records of ocean heat cont ent cover; sea ice; level atmospheric water Scientists from all over the world have independently vericover; sea ice; sea level and atmospheric water vapour. Scientists from all over the world have independently verigoing back t o t he 1950s. (continued on next page) ﬁﬁed edthis thisevidence evidencemany manytimes. times.that Thatthe theworld worldhas haswarmed warmedsince sincethe the19th 19thcentury centuryisisunequivocal. unequivocal. Discussion Discussionabout about climate climatewarming warmingoften oftencentres centreson onpotential potentialresidual residualbiases biasesinintemperature temperaturerecords recordsfrom fromlandlandbased weather stations. These records are very important, but they only represent one indicator of changes in the based weather stations. These records are very important, but they only represent one indicator of changes in the Glacier Volume climate system.airbroader Temperature evidence for a warming world comes from a wide range of independent physically consisclimate system. evidence for a warming world comes from a wide range of independent physically consisin thebroader lowest few Km (troposphere) tent measurements of many other, strongly interlinked, elements of the climate system (F AQ 2.1, Figure 1). tent measurements of many other, strongly interlinked, elements of the climate system (F AQ 2.1, Figure 1). Water Vapor Temperature A rise in global average surf ace t emperatures is the best-known indicator of climate change. Although each year and Land A rise in global average surface temperatures is theover best-known indicator of climate change. Although each year and even decade is not always warmer than the last, global surface temperatures have warmed substantially since 1900. Sea Ice Area even decade is not always warmer than the last, global surface temperatures have warmed substantially since 1900. Warming land temperatures correspond closely with the observed warming trend over the oceans. Warming ocesnow Cover Warming land correspond closely with the observed warming trend over the oceans. Warming ocemarinetemperatures Air Temperature anic air temperatures, measured from aboard ships, and temperatures of the sea surface itself also coincide, as anic air temperatures, measured from aboard ships, and temperatures of the sea surface itself also coincide, as borne out by many independent analyses. Surface borne Sea out by Temperature many independent analyses. The atmosphere and ocean are both ﬂ uid bodies, so warming at the surface should also be seen in the lower atmothe atmosphere and ocean are Sea both Level ﬂ uid bodies, so warming at the surface should also be seen in the lower atmosphere, and deeper down into the upper oceans, and observations conﬁ rm that this is indeed the case. Analyses of sphere, and deeper down into the upper oceans, and observations conﬁ rm that this is indeed the case. Analyses of measurements made by weather balloon radiosondes and satellites consistently show warming of the troposphere, measurements made by weather balloon radiosondes and satellites consistently show warming of the troposphere, the active weather layer of the atmosphere. More than 90% of the excess energy absorbed by the climate system Ocean Heat the active weather layer of Content the atmosphere. More than 90% of the excess energy absorbed by the climate system since at least the 1970s has been stored in the oceans as can be seen from global records of ocean heat content since at least the 1970s has been stored in the oceans as can be seen from global records of ocean heat content going back to the 1950s. (continued on next page) going back to the 1950s. (continued on next page) FAQ 2.1, Figure 1 Independent analyses of many components of the climate system that would be expected to change in a warming world exhibit trends consistent with warming (arrow direction denotes the sign of the change), as shown in FAQ 2.1, Figure 2. 7 Air Temperature inair the Temperature lowest few Km (troposphere) Glacier Volume Glacier Volume in the lowest few Km (troposphere) Water Vapor Water Vapor Temperature Temperature Over Land Over Land FAQ FAQ

WGII AR5

WGIIAR5

WGIIIAR5

More on Design and Format Pose questions and provide answers in a neutral rather than leading manner. Avoid a defensive tone. Answer needs to be consistent with underlying material in the chapter popularisation of text should not reduce rigour A few additional Style Guide details: Cross-references to chapter sections(s), but no external citations/references Length: Total length up to ~1 IPCC pages, up to 1 printed IPCC page of text (~950 words), one engaging figure (optional?).

Proposed Process and Timetable. Chapter Teams discuss a preliminary set of potential questions (~3) for their chapter at LAM1 and forward to WGI TSU by end of LAM1 Co-Chairs (with TSU) will liaise with CLAs to choose 1-2 FAQs per chapter and proposed wording for the Questions CLAs select a lead LA for each FAQ in their chapter Chapter teams produce an initial draft of each FAQ for the Internal Draft

WGIIAR5

WGIIIAR5