Organisation Météorologique mondiale publie un rapport alarmant sur les événements météo

Description

Rendu publique mardi 8 novembre à Marrakech, à la COP22, une analyse détaillée du climat mondial de 2011 à 2015 - le quinquennat le plus chaud jamais enregistré.

Sujets

• Marrakech
• Organisation météorologique mondiale
• Rapport
• COP
• Organisation météorologique internationale

Informations

• Publié par: Fil_actu
• Publié le: 09 novembre 2016
• Nombre de lectures: 11
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

The Global Climate in 2011–2015

WEATHER CLIMATE WATER

WMONo. 1179

WMONo. 1179 © World Meteorological Organization, 2016

The rîght o publîcatîon în prînt, electronîc and any other orm and în any language îs reserved by WMO. Short extracts rom WMO publîcatîons may be reproduced wîthout authorîzatîon, provîded that the complete source îs clearly îndîcated. Edîtorîal correspondence and requests to publîsh, reproduce or translate thîs publîcatîon în part or în whole should be addressed to:

Chaîrperson, Publîcatîons Board World Meteorologîcal Organîzatîon (WMO) 7 bîs, avenue de la Paîx P.O. Box 2300 CH-1211 Geneva 2, Swîtzerland

ISBN 978-92-63-11179-1

Tel.: [phone] Fax: [phone] E-maîl: publîcatîons@wmo.înt

WMO, în collaboratîon wîth Members, began îssuîng annual statements on the status o the global clîmate în 1993. Thîs publîcatîon was îssued în collaboratîon wîth the Arîcan Centre o Meteorologîcal Applîcatîons or Development (ACMAD), Nîger; European Centre or Medîum-Range Weather Forecasts (ECMWF), Unîted Kîngdom o Great Brîtaîn and Northern Ireland; Japan Meteorologîcal Agency (JMA); Met Oice Hadley Centre, Unîted Kîngdom; Clîmatîc Research Unît (CRU) at the Unîversîty o East Anglîa, Unîted Kîngdom; Clîmate Predîctîon Center (CPC), the Natîonal Centers or Envîronmental Inormatîon (NCEI) and the Natîonal Hurrîcane Center (NHC) o the Natîonal Oceanîc and Atmospherîc Admînîstratîon (NOAA), Unîted States o Amerîca; Natîonal Aeronautîcs and Space Admînîstratîon, Goddard Instîtute or Space Studîes (NASA GISS), Unîted States; Global Precîpîtatîon Clîmatology Centre (GPCC), Deutscher Wetterdîenst, Germany; Natîonal Snow and Ice Data Center (NSIDC), Unîted States; Commonwealth Scîentîfic and Industrîal Research Organîzatîon (CSIRO) Marîne and Atmospherîc Research, Australîa; Global Snow Lab, Rutgers Unîversîty, Unîted States; Internatîonal Research Centre on El Nîño (CIIFEN), Ecuador; Royal Netherlands Meteorologîcal Instîtute (KNMI), Netherlands; Instîtute on Global Clîmate and Ecology (IGCE), Russîan Federatîon; All-Russîan Research Instîtute or Hydrometeorologîcal Inormatîon – World Data Center (ARIHMI-WDC), Russîan Federatîon;Bulletin of the American Meteorological Society, annual State o the Clîmate reports; Centre or Research on the Epîdemîology o Dîsasters (CRED), Unîversîté catholîque de Louvaîn, Belgîum; World Glacîer Monîtorîng Servîce, Unîversîty o Zurîch, Swîtzerland; Joînt Typhoon Warnîng Center (JTWC), Honolulu, Unîted States; Natîonal Instîtute or Space Research (INPE), Brazîl; Nîger Basîn Authorîty, Nîamey; Intergovernmental Authorîty on Development (IGAD) Clîmate Predîctîon and Applîcatîons Centre (ICPAC), Naîrobî; WMO Regîonal Clîmate Centres în Europe, Asîa (Tokyo Clîmate Center), southern and western South Amerîca, and eastern and northern Arîca; WMO Global Atmosphere Watch and Global Cryosphere Watch programmes; World Food Programme (WFP); Unîted Natîons Envîronment Programme (UNEP); and Oice o the Hîgh Commîssîoner or Reugees (UNHCR). Other contrîbutors are the Natîonal Meteorologîcal and Hydrologîcal Servîces or equîvalent o: Algerîa; Antîgua and Barbuda; Argentîna; Armenîa; Australîa; Austrîa; Azerbaîjan; Barbados; Belarus; Belgîum; Bosnîa and Herzegovîna; Brazîl; Bulgarîa; Burkîna Faso; Canada; Chîle; Chîna; Colombîa; Croatîa; Cuba; Cyprus; Czechîa; Denmark (încludîng Greenland); Domînîcan Republîc; Egypt; Estonîa; Ethîopîa; Fîjî; Fînland; France (încludîng French Pacîfic, Carîbbean and Indîan Ocean terrîtorîes); Germany; Haîtî; Hong Kong, Chîna; Hungary; Iceland; Indîa; Indonesîa; Iran, Islamîc Republîc o; Ireland; Israel; Italy; Jamaîca; Japan; Jordan; Kenya; Lîbya; Lîthuanîa; Luxembourg; Madagascar; Malawî; Malaysîa; Malî; Maurîtîus; Mexîco; Montenegro; Morocco; Netherlands; New Zealand; Nîger; Norway; Pakîstan; Panama; Papua New Guînea; Paraguay; Peru; Phîlîppînes; Poland; Qatar; Republîc o Korea; Republîc o Moldova; Russîan Federatîon; Saînt Lucîa; Senegal; Serbîa; Seychelles; Sîngapore; Slovakîa; Slovenîa; South Arîca; Spaîn; Sudan; Sweden; Swîtzerland; Thaîland; Turkey; Ukraîne; Unîted Kîngdom; Unîted Republîc o Tanzanîa; Unîted States; Uruguay; and Vanuatu.

Cover îllustratîon: Mykola Mazuryk (Adobe Stock)

NOTE

The desîgnatîons employed în WMO publîcatîons and the presentatîon o materîal în thîs publîcatîon do not împly the expressîon o any opînîon what- soever on the part o WMO concernîng the legal status o any country, terrîtory, cîty or area, or o îts authorîtîes, or concernîng the delîmîtatîon o îts rontîers or boundarîes.

The mentîon o specîfic companîes or products does not împly that they are endorsed or recommended by WMO în preerence to others o a sîmîlar nature whîch are not mentîoned or advertîsed.

The findîngs, înterpretatîons and conclusîons expressed în WMO publîcatîons wîth named authors are those o the authors alone and do not neces- sarîly reflect those o WMO or îts Members.

Contents

Foreword                                              3

Executîve summary                                        5

Key findîngs                                             6

The world’s warmest five-year perîod on record . . . . . . . . . . . . . . . . . . . . . . 6

Concentratîon o long-lîved greenhouse gases contînues to încrease . . . . . . . . . . 8

Wîdespread meltîng o îce except în the Southern Ocean . . . . . . . . . . . . . . . . . 9

Sea levels contînue to rîse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Precîpîtatîon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Large-scale modes o clîmate varîabîlîty . . . . . . . . . . . . . . . . . . . . . . . . . .16

Major extreme events o the perîod 2011–2015 . . . . . . . . . . . . . . . . . . . . . . .16

Heatwaves a regular occurrence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Despîte overall warmth, some perîods o sîgnîficant cold and snow . . . . . . . . . . .19

Destructîve floodîng în many parts o the world . . . . . . . . . . . . . . . . . . . . . .20

Prolonged droughts afected several contînents . . . . . . . . . . . . . . . . . . . . . .21

Tropîcal cyclones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Damagîng tornadoes and wîndstorms . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Anthropogenîc clîmate change contrîbuted to some extreme events . . . . . . . . . .25

Antarctîc ozone hole stabîlîzes, but no strong evîdence o recovery yet . . . . . . . . .27

>US$ 67 billion

Probability that climate change affected occurrence of many extremes

>7 800

>250 000

Economic losses attributed to HurricaneSandy, 2012

Record minimum Arctic seaice extent in 2012

Excess deaths attributed to drought and famine in 2011–2012 in the Horn of Africa

Deaths attibuted to heatwaves in Pakistan and India, 2015

2

2011–2015

Warmest fiveyear period on record

>4 100

X10 EXTREME EVENTS

Deaths in Philippines attributed to TyphoonHaiyan (Yolanda), 2013

3.39 2 million km

Foreword

Thîs report descrîbes the evolutîon o the clî- mate system durîng the perîod 2011–2015. The World Meteorologîcal Organîzatîon (WMO) has assessed thîs five-year perîod în order to contrîbute to a better understandîng o multî- year warmîng trends and extreme events that can help governments to împlement the Unîted Natîons Framework Conventîon on Clîmate Change more efectîvely. Thîs applîes în par- tîcular to the 2015 Parîs Agreement, whîch provîdes a hîstorîc opportunîty or the global communîty to act wîth greater urgency în curbîng greenhouse gas emîssîons, osterîng clîmate resîlîence and maînstreamîng clîmate adaptatîon înto natîonal development polîcîes.

W hî l e t h e Pa r î s Ag r e e me n t e n g a g e s governments în pursuîng eforts to lîmît the global temperature încrease to 1.5 °C above pre-îndustrîal levels, thîs report confirms that the average temperature în 2015 had already rîsen by more than one degree (wîth 2016 on track to be even warmer) sînce the pre- îndustrîal perîod. The report also conîrms that the perîod 2011–2015 was the warmest îve-year perîod on record, consîstent wîth establîshed long-term warmîng trends due to rîsîng levels o greenhouse gases. In addîtîon, ît notes that many îndîvîdual extreme weather and clîmate events recorded durîng 2011–2015 had theîr lîkelîhood o occurrîng substantîally enhanced by human-înduced clîmate change. Thîs evîdence o clîmate change demonstrates the împortance o takîng îmmedîate actîon under the Parîs Agreement.

An advantage o a medîum-term perspectîve îs that ît makes ît possîble to take înto account multî-year events such as prolonged droughts and recurrent heatwaves. Thîs tîme rame also enables scîentîsts and decîsîon-makers to more rîgorously assess the valîdîty o mîd- and long- term projectîons o anthropogenîc clîmate change through the persîstence o extreme phenomena.

Thîs five-year report expands on the approach taken by WMO sînce 1993 în consolîdatîng the best avaîlable clîmate înormatîon rom

Natîonal Meteorologîcal and Hydrologîcal Servîces înto yearly statements on the status o the global clîmate. In 2013, WMO îssued a decadal clîmate summary coverîng the perîod 2001–2010. Sînce 2006, WMO has also produced annual Greenhouse Gas Bulletîns that report on atmospherîc concentratîons o the greenhouse gases that drîve clîmate change.

The early efects o clîmate change have been consîstently vîsîble on the global scale sînce the 1980s: the încrease o the global temperature, both over land and în the surace and deep ocean; sea-level rîse; and the wîdespread meltîng o îce (wîth the înterestîng exceptîon o the Southern Ocean). In addîtîon, the înfluence o clîmate change on the daîly lîves o people has been clear due to the multîplîcatîon and întensîficatîon o extreme events, încludîng heatwaves to record raînall and damagîng floods.

The WMO multî-year repor ts and annual statements on the state o the clîmate com- plement the assessments reports o the WMO/ Unîted Natîons Envîronment Programme Intergovernmental Panel on Clîmate Change (IPCC). They aîm to înorm governments, înter- natîonal agencîes and other WMO partners on a more requent basîs about global clîmate trends and extreme weather and clîmate events at the natîonal and regîonal levels.

We belîeve that thîs report, together wîth those to ollow, wîll help to strengthen the scîen- tîîc oundatîon or împlementîng the Parîs Agreement and adjustîng natîonal polîcîes as needed to reflect changîng clîmate condîtîons.

(P. Taalas) Secretary-General

3

Executive summary

The five-year perîod rom 2011 to 2015 has been the warmest five-year perîod on record globally, wîth 2015 beîng the warmest year on record 1 to date. The perîod 2011–2015 was also the warmest on record or every contînent except Arîca. Durîng thîs perîod, concentratîons o the major greenhouse gases contînued to rîse and reached record levels or the înstrumental perîod.

The record hîgh temperatures rom 2011 to 2015, along wîth the annual record set în 2015, are consîstent wîth establîshed long-term warm- îng trends, the domînant cause o whîch îs the emîssîon o anthropogenîc greenhouse gases. Year-to-year temperature fluctuatîons occur agaînst the backdrop o the long-term warmîng trend, în partîcular as a result o El Nîño and La Nîña events. Hîgh temperatures have been accompanîed by the contînuatîon o long-term trends în other îndîcators that are consîstent wîth warmîng, such as rîsîng sea levels and declînes în Arctîc sea-îce extent and în contînental glacîers and îce sheets în Arctîc and hîgh-mountaîn regîons.

The sîngle most sîgnîficant event o the perîod în humanîtarîan terms was the 2011–2012 amîne în the Horn o Arîca, to whîch drought în late 2010 and 2011 was a major contrîbutor. More than 250 000 excess deaths în the Horn o Arîca were attrîbuted to thîs event by the Famîne Early Warnîng Systems Network. On shorter tîmescales, no sîngle clîmate-related dîsaster în the perîod 2011–2015 was assocîated wîth short-term casualtîes on the scale o some o the worst events o the prevîous decade, such as the 2003 European heatwave and Cyclone Nargisîn Myanmar în 2008. However, many o the worst dîsasters o the perîod 2011–2015 stîll învolved extreme weather and clîmate. Three tropîcal cyclones – încludîng one împlîcated în the perîod’s worst sîngle meteorologîcal dîsaster, TyphoonHaiyan (Yolanda)– were each assocî- 2 ated wîth over 1 000 deaths în the Phîlîppînes.

1  At the tîme o wrîtîng, ît îs lîkely that the 2015 record hîgh annual temperature wîll be exceeded în 2016.

2  Unless otherwîse stated, casualty figures în thîs publîcatîon are sourced rom the EM-DAT Emergency Events Database maîntaîned by the Centre or Research on the Epîdemîology o Dîsasters at the Unîversîté catholîque de Louvaîn, Belgîum.

Casualtîes were on a comparable scale în Indîa and Pakîstan due to floodîng în 2013 and heat- waves în 2015. The South-East Asîan floodîng o 2011 and HurrîcaneSandyîn the Carîbbean (espe- cîally Haîtî) and the Unîted States o Amerîca în 2012 both resulted în economîc losses în excess 3 o US$ 40 bîllîon.

Scîentîfic assessments have ound that many extreme events în the perîod 2011–2015, especîally those învolvîng ex treme hîgh temperatures, have had theîr probabîlîtîes sub- stantîally încreased, by a actor o 10 or more în some cases, as a result o anthropogenîc clîmate change. More than hal the events assessed scîentîfically manîested some degree o anthro- pogenîc clîmate change sîgnal. In addîtîon, there have been longer-term events that have not yet been the subject o ormal attrîbutîon studîes but that are consîstent wîth projectîons o near- and long-term clîmate change. These înclude, or example, încreased încîdence o multî-year drought în the subtropîcs, as manî- ested durîng the perîod în the southern Unîted States, parts o southern Australîa and, towards the end o the perîod, southern Arîca. There also have been events, such as the unusually prolonged, întense and hot dry seasons în the Amazon basîn o Brazîl, în both 2014 and 2015 (especîally the latter). Whîle they cannot yet be stated wîth confidence to be part o a long- term trend, these are o consîderable concern în the context o potentîal “tîppîng poînts” în the clîmate system as îdentîfied by the IPCC Fîth Assessment Report.

The present assessment descrîbes the state o the key components o the clîmate system în the 4 perîod 2011–2015. It ocuses on events such as multî-year droughts that requîre a longer-term perspectîve than îs possîble în an annual report.

3  Economîc loss estîmates or thîs event are rom the World Bank or the South-East Asîan floodîng în 2011, and rom the Natîonal Oceanîc and Atmospherîc Admînîstratîon Natîonal Centers or Envîronmental Inormatîon (NOA A NCEI) or HurrîcaneSandy.

4  Some înormatîon îs also încluded rom events în late 2010 that extended înto 2011, lîkewîse 2015 events that extended înto early 2016.

5

Figure 1. Global annual average temperature anomalîes (relatîve to 1961–1990) or 1850 – 2015. The black lîne and grey shadîng are rom the HadCRUT4 analysîs produced by the Met Oice Hadley Centre în collaboratîon wîth the Clîmatîc Research Unît at the Unîversîty o East Anglîa. The grey shadîng îndîcates the 95% confidence înterval o the estîmates. The orange lîne îs the NOA AGlobalTemp dataset produced by NCEI. The blue lîne îs the GISTEMP dataset produced by NASA GISS. (Source: Met Oice Hadley Centre, Unîted Kîngdom, and Clîmatîc Research Unît, Unîversîty of East Anglîa, Unîted Kîngdom)

6

Key findings

0.5

0

– 0.5

Met Oce Hadley Centre and Climatic Research Unit NOAA National Centers for Environmental Information NASA Goddard Institute for Space Studies

Global average temperature anomaly (°C)

1850

1900

THE WORLD’S WARMEST FIVEYEAR PERIOD ON RECORD

The perîod 2011–2015 was the warmest five-year 5 perîod on record globally. Usîng the mean o 6 three major global datasets, temperatures or the perîod were 0.57 °C (1.03 °F) above the aver- age or the standard 1961–1990 reerence perîod. Thîs compares wîth the perîod 2006–2010, în

5  For the purposes o thîs report, five-year perîods are defined as those five-year perîods endîng în a year endîng în 5 or 0, or example, 2011–2015, 2006–2010, 2001–2005. However, global temperatures or 2011–2015 are hîgher than those o any other five-year perîod whether or not such a restrîctîon îs applîed. The next hîghest unrestrîcted five-year average îs 0.54 °C above the 1961–1990 average, set în 2010 –2014.

6  Global temperature anomalîes are computed usîng three global datasets: HadCRUT4.4, joîntly produced by the Met O îce Hadley Centre and the Clîmatîc Research Unît at the Unîversîty o East Anglîa, Unîted Kîngdom; the GISTEMP analysîs (2016 versîon), produced by the Natîonal Aeronautîcs and Space Admînîstratîon Goddard Instîtute or Space Studîes (NASA GISS); and the NOA A Merged Land Ocean Global Sur ace Temperature Analysîs Dataset (versîon 4.0), produced by NCEI. Contînental temperature anomalîes use NOAA data only, whîle natîonal and sub-natîonal anomalîes use data supplîed by the relevant Natîonal Meteorologîcal or Hydrologîcal Servîce unless otherwîse stated.

Year

1950

2000

whîch temperatures were 0.51 °C (0.92 °F) above average, and îs consîstent wîth a contînued sustaîned warmîng trend that has been apparent în global data sînce the mîd-1970s.

The warmest year on record to date was 2015, durîng whîch temperatures were 0.76 °C (1.37 °F) above the 1961–1990 average. The year 2015 was also the first year în whîch global temperatures were more than 1 °C above the 7 pre-îndustrîal average. The second-warmest year was 2014, whîch was 0.61 °C (1.10 °F) above the 1961–1990 average, whîle 2013 ranks as the equal-fith warmest year. Substantîally înfluenced by La Nîña events (especîally the ormer), 2011 and 2012 were somewhat less warm but stîll warmer than any year prîor to 1998, and warmer than any prevîous La Nîña year. The world’s 12 warmest years have all occurred sînce 1998, 9 o them sînce 2005. Whîle the hîgh temperatures în 2015 were înfluenced by the El Nîño event that developed durîng that year, the împact o El Nîño on global temperatures îs typîcally stronger în the second year o the event than în the first. Thus, the

7  A number o deînîtîons are used by varîous sources or pre-îndustrîal. The most commonly used are 1850 –1900 and 1880 –1900. The 2015 status holds or eîther o these baselîne perîods.



4



4Ś

90S 180

✁ �➊

➊ ✂

➊✄

90W

0

90E

  3 ➊�➊✁☎✂☎✆➊✁✆☎✁✁✂☎ Temperature dierence (°C) compared to the 1961–1990 average

prîmary împact o the 2015–2016 El Nîño on annual global temperatures îs expected to be 8 în 2016 rather than 2015.

Warmth was wîdespread around the world throughout the perîod, both on land and în the ocean. Temperatures or the perîod 2011–2015 were more than 1 °C above the 1961–1990 aver- age over most o Europe, the Asîan part o the Russîan Federatîon and most remaînîng areas north o 60 °N, reachîng 3 °C above aver- age locally on the Arctîc coast o the Russîan Federatîon. They were also more than 1 °C above average over much o the Saharan and Arabîan regîons, parts o Southern Arîca, the south- west Unîted States and north-west Mexîco, and în înterîor Brazîl. No large land areas were consîstently cool through the five-year perîod, although some experîenced îndîvîdual cool years, or example, northern Australîa în 2011 and 2012, central North Amerîca în 2013 and 2014, and central Asîa and Alaska în 2012.

It was the warmest five-year perîod on record or Europe, South Amerîca, Asîa, Oceanîa and North Amerîca, where record warm condîtîons

8  Mean temperatures or January–July 2016 were 0.91 °C (1.64 °F) above the 1961–1990 average and 0.15 °C (0.27 °F) above the 2015 annual anomaly.



180



în the west ofset near-average temperatures în parts o the east, and ranked second or Arîca. The temperatures în Europe or that same perîod were 1.29 °C above the 1961–1990 average, 0.26 °C warmer than any prevîous five-year perîod. South Amerîca and Asîa experîenced theîr warmest year on record în 2015, Europe în 2014 and Oceanîa în 2013. Notable seasonal anomalîes încluded the warmest sprîng on record or North Amerîca (2012) and Europe, South Amerîca and Oceanîa (all 2014); the hot- test summer on record or North Amerîca (2012), South Amerîca and Oceanîa (both 2015 and 2016); the warmest autumn and wînter on record or South Amerîca (both 2015); the warmest autumn on record or North Amerîca (2015); and the warmest June–August and September– November on record or Arîca (2015).

A partîcularly noteworthy eature o the perîod 2011–2015 was the occurrence o îndîvîdual years în whîch records were set by large margîns în substantîal land areas. Prevîously exîstîng records or annual mean temperatures were broken by between 0.17 °C and 0.40 °C în the contînental Unîted States în 2012, Australîa în 2013, Europe în 2014 and South Amerîca în 2015.

Global ocean temperatures were also at unprec- edented levels. Globally averaged sea-surace temperatures or 2015 were the hîghest on

Figure 2. Global five-year average temperature anomalîes (relatîve to 1961–1990) or 2011– 2015. The analysîs uses HadCRUT4 analysîs produced by the Met Oice Hadley Centre în collaboratîon wîth the Clîmatîc Research Unît at the Unîversîty o East Anglîa, Unîted Kîndgdom.

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Figure 3. Average temperature anomalîes în the sîx contînental regîons (Source: Data used are from NOAA NCEI)

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1.5

1

0.5

0

Temperature anomaly (°C) – 0.5

– 1

Europe Oceania Asia Arica South America North America

19119–11699–1215199–22101699–2315199–33101699–3415199–44101699–451199–55101699–5615199–66101699–6715199–77101699–7815199–88101699–891519–99102690–90252100–022600–12510–120015

Year

record or a calendar year, with 2014 in sec- ond place. Sea-surace temperatures or the period were above average în most o the world, although they were below average în parts o the Southern Ocean and the eastern South Pacîfic. Areas where 2011–2015 was the warmest five-year perîod on record înclude most o the South Indîan Ocean, the Southern Ocean south o Australîa, the central and eastern North Pacîfic, the western equatorîal Pacîfic, most o the western hal o the North Atlantîc north o the tropîcs, parts o the subtropîcal western South Atlantîc, and the Medîterranean Sea.

Two notable ocean temperature anomalîes developed rom late 2013 onward: a large area o very warm water în the eastern North Pacîfic, wîth sea-surace temperatures more than 2 °C above average în places, and a persîstent pool o below-normal sea-surace temperatures în the eastern North Atlantîc between the Brîtîsh Isles and the southern tîp o Greenland.

CONCENTRATION OF LONGLIVED GREENHOUSE GASES CONTINUES TO INCREASE

The concentratîon o major long-lîved green- house gases în the atmosphere contînued to încrease durîng the perîod 2011–2015.

9 In 2015, the annual mean concentratîons în the atmosphere o carbon dîoxîde (CO ), methane 2 (CH ) and nîtrous oxîde (N O) were, 400.0 parts 4 2 per mîllîon (ppm), 1 845 parts per bîllîon (ppb) and 328.0 ppb, respectîvely (CO îs responsîble 2 or about 65% o the total radîatîve orcîng rom

9  These concentratîons are averaged through the whole year and across all suîtable statîons reportîng as part o the WMO Global Atmosphere Watch. The annual cycle o CO îs approxîmately 2 6-ppm magnîtude, wîth concentratîons at the seasonal peak în Aprîl and May typîcally about 3 ppm hîgher than the annual mean.

410 (a) 400 390 380 370 360 2 mo 3 l 5 e 0 raction (ppm) 340 CO 330 1985 1990 1995 2000 2005 2010 2015 Year 4 (b)

3

2

gr 1 owth rate (ppm/yr) 2 CO 0 1985 1990 1995 2000 2005 2010 2015 Year

1900 (a) 1850

1800

1750

1700 mole raction (ppb) 4 1650 CH 1600 1985 1990 1995 2000 2005 2010 2015 Year 20 (b) 15

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5 growth rate (ppb/yr) 4 0 CH -5 1985 1990 1995 2000 2005 2010 2015 Year

lonor aboutg-lîved greenhouse gases, CH 4 17% and N O or 6%). 2

These concentratîons încreased consîstently throughout the perîod rom 2011 onward, wîth annual rates o încrease rangîng between 1.9 and 2.9 ppm per year between 2011 and 2015 or CO , between 5 and 9 ppb per year or CH 2 4 and about 1 ppb or N O. The rate o încrease 2 o CO concentratîons încreased în 2015 and 2 reached 2.3 ppm per year, whîle CH (11 ppb 4 per year) showed îts strongest annual growth sînce 1998. The growth rates observed or CO 2 and N O rom 2011 to 2015 are slîghtly hîgher 2 than the 1995–2015 average, whîle those or CH 4 reflect a renewed perîod o growth ollowîng a perîod o lîttle change în CH concentratîons 4 rom 1999 to 2006.

The 2015 Greenhouse Gas Bulletîn shows that approxîmately 44% o the total CO 2 emîtted by human actîvîty rom 2004 to 2015 remaîned în the atmosphere, wîth the remaîn- îng 56% removed by oceans and the terrestrîal bîosphere.

WIDESPREAD MELTING OF ICE EXCEPT IN THE SOUTHERN OCEAN

Arctîc sea îce contînued îts declîne în the perîod 2011–2015. The mînîmum summer sea-îce extent 2 o 3.39 mîllîon km în 2012 was the lowest on

330 (a) 325 320 315 310 O mole raction (ppb) 2 305 N 300 1985 1990 1995 2000 2005 2010 2015 Year 2 (b)

1.5

1

0.5 O growth rate (ppb/yr) 2 N 0 1985 1990 1995 2000 2005 2010 2015 Year

record. The summer sea-îce extent or 2011 was the thîrd lowest and or 2015 the ourth lowest or the post-1979 satellîte record. The mean Arctîc sea-îce extent în September, normally the month wîth the smallest sea-îce extent, 2 în the perîod 2011–2015 was 4.70 mîllîon km , 28% below the 1981–2010 average and lower than the prevîous lowest five-year average o 2 5.04 mîllîon km în 2006–2010. Arctîc sea îce has not been declînîng as rapîdly în wînter as ît has în summer, but nevertheless the lowest 2 wînter maxîmum on record, 14.54 mîllîon km , was în 2015. The wînter maxîmum extents were below the 1981–2010 mean în all five years rom 2011 to 2015.

By contrast, or much o the perîod 2011– 2015, the Antarctîc sea-îce extent was above the 1981–2010 mean value, partîcularly or the wînter maxîmum. In September 2014, the sea-îce extent în the Southern Ocean 2 2 reached 20.16 mîllîon km , 1.45 mîllîon km above the 1981–2010 average and the hîgh- est value în the satellîte record. The 2013 and 2012 maxîma ranked second and thîrd, respectîvely. However, an abnormally slow wînter reeze-up în 2015 resulted în sea-îce extent returnîng to near-average levels by sprîng 2015, wîth the 2015 maxîmum (în early 2 October) o 18.83 mîllîon km , only 0.7% above the 1981–2010 average. The observed long- term încrease în Antarctîc sea îce sînce 1979

Figure 4. Globally- averaged mole ractîons (a measure o concentratîon) o CO în 2 parts per mîllîon (let), CH în parts per bîllîon 4 (mîddle) and N O în 2 parts per bîllîon (rîght); the perîod 1985 –2015 îs shown on the top row wîth grow th rates on the bot tom row; annually averaged grow th rates shown as columns în the bot tom row o plots

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