INFLUENCE OF FOREST COVERAGE IN THE SURFACE ALBEDO

The surface albedo controls the energy balance between the surface and the atmosphere, being a primordial variable to identify climatic variations. The objective of this study was to evaluate the changes of the surface albedo in different Land Use and Land Cover in the Atlantic Forest biome from images TM/Landsat 5 and OLI/Landsat 8, verifying its variation in 30 years. The images used were path-row 221-080, which covered the Floresta Nacional de São Francisco de Paula on the dates of 1987 and 2017. The albedo was obtained by the method of the Surface Energy Balance Algorithm for Land, while the mapping of Land Use and Land Cover was performed by the Bhattacharyya algorithm, identifying four thematic classes. Finally, the albedo was crossed with the thematic classes, evidencing their variation in function of the changes in the land cover. The surface albedo ranged from 6 to 22%, but the year 1987 concentrated albedo values higher than in 2017. The native forest presented superior albedo to the Forest Plantations in both dates due to the structure of the canopy of this class. The spatial analysis of the albedo exposes the relation of this climatic variable to the cover of the terrestrial surface. Thus changes in the vegetation cover cause alterations in the albedo, influencing changes in the radiation and atmospheric fluxes

Tärkeiden ilmastonmuutosta ja -vaihteluita aiheuttavien prosessien mallintaminen

Greenhouse gas warming, internal climate variability and aerosol climate effects are studied and the importance to understand these key processes and being able to separate their influence on the climate is discussed. Aerosol-climate model ECHAM5-HAM and the COSMOS millennium model consisting of atmospheric, ocean and carbon cycle and land-use models are applied and results compared to measurements. Topics at focus are climate sensitivity, quasiperiodic variability with a period of 50-80 years and variability at other timescales, climate effects due to aerosols over India and climate effects of northern hemisphere mid- and high-latitude volcanic eruptions. The main findings of this work are 1) pointing out the remaining challenges in reducing climate sensitivity uncertainty from observational evidence, 2) estimates for the amplitude of a 50-80 year quasiperiodic oscillation in global mean temperature ranging from 0.03 K to 0.17 K and for its phase progression as well as the synchronising effect of external forcing, 3) identifying a power law shape S(f) ∝ f−α for the spectrum of global mean temperature with α ∼ 0.8 between multidecadal and El Nino timescales with a smaller exponent in modelled climate without external forcing, 4) separating aerosol properties and climate effects in India by season and location 5) the more efficient dispersion of secondary sulfate aerosols than primary carbonaceous aerosols in the simulations, 6) an increase in monsoon rainfall in northern India due to aerosol light absorption and a probably larger decrease due to aerosol dimming effects and 7) an estimate of mean maximum cooling of 0.19 K due to larger northern hemisphere mid- and high-latitude volcanic eruptions. The results could be applied or useful in better isolating the human-caused climate change signal, in studying the processes further and in more detail, in decadal climate prediction, in model evaluation and in emission policy design in India and other Asian countries.Ilmastonmuutosta ja ilmastonvaihteluita tutkittiin erilaisilla ilmastomalleilla, päätyökalujen ollessa Max Planck Institutilla kehitetty aerosolimalli ja ilmastojärjestelmämalli, joita ajetaan supertietokoneilla. Aiheet liittyivät ilmaston lämpenemiseen kasvihuonekaasujen takia, ilmaston sisäiseen vaihteluun sekä pienhiukkasten ilmastovaikutuksiin. Väitöskirjan päätuloksia: 1) Ilmaston herkkyys, eli maapallon keskilämpötilan kohoaminen hiilidioksidipitoisuuden kaksinkertaistuessa, on edelleen epävarma suure ja etenkin suurten arvojen poissulkeminen on vaikeaa havaintojen perusteella. Tämän takia tietyllä hiilidioksidipitoisuudella ilmaston lämpeneminen on jollakin todennäköisyydellä parasta arviota huomattavasti voimakkaampaa, 2) Maapallon ilmasto näyttäisi mittausten ja mallikokeiden perusteella muuttuvan n. 65 vuoden (50-80) kvasisäännöllisissä heilahteluissa (muiden muutosten ja vaihteluiden lisäksi). Heilahtelun amplitudi on todennäköisesti n. 0,05-0,15 astetta maapallon keskilämpötilassa ja fysikaaliset syyt liittyvät valtamerten hitaaseen dynamiikkaan, 3) Käytetty ilmastojärjestelmämalli simuloi ilmastonvaihtelut mittauksiin verrattuna hyvin eri taajuuksilla noin 65 vuoden heilahteluista 3-7 vuoden El Nino -heilahteluihin, 4) Intian ja Kiinan pienhiukkasten jakaumat ajan, paikan, hiukkasen koon ja kemiallisen koostumuksen suhteen mallisimulaatioissa nykypäästöillä sekä eräitä tulevaisuusskenaarioita käyttäen, 5) Jos pienhiukkanen muodostuu kaasusta ilmakehässä, se näyttäisi ainakin Intiassa ja Kiinassa kulkeutuvan keskimäärin kauemmaksi lähdealueistaan kuin suoraan poltto- tai mekaanisissa prosesseissa syntyvät pienhiukkaset, 6) Pohjois-Intian monsuunisateet vähenevät mallisimulaatioiden perusteella pienhiukkasten valoa himmentävästä vaikutuksesta johtuen, vaikka valon absorptio lisää sitä, 7) Arviot tietynsuuruisten pohjoisen pallonpuoliskon keski- ja korkeiden leveysasteiden tulivuorenpurkausten keskimäärin aiheuttamille ilmastovaikutuksille, mm. maksimiviileneminen 0,19 astetta pallonpuoliskon keskilämpötilassa.Uppvärmning av klimatet p.g.a. växthusgaser, intern variabilitet av klimatet och klimateffekter av aerosoler studeras och vikten av att förstå och kunna kvantifiera dessa processer diskuteras. Aerosolklimatmodellen ECHAM5-HAM och COSMOS-milleniummodellen, som består av atmosfär-, ocean- och landsanvändnings- och kolkretsloppsmodeller, tillämpas och resultat jämförs med observationer. Ämnen som avhandlingen koncentrerar sig på är klimatkänsligheten, kvasiperiodisk variabilitet med en period på 50-80 år och variabilitet med andra tidsskalor, klimateffekter och egenskaper av aerosoler i Indien och klimateffekter av vulkanutbrott vid höga och medelhöga breddgrader av det norra halvklotet. De viktigaste upptäckterna i denna avhandling är 1) påvisandet av de återstående utmaningarna i att minska osäkerheten av klimatkänsligheten uppskattad från observationer, 2)uppskattningar av amplituden av en kvasi-periodisk 50-80 årig oskillation i den globala medeltemperaturen från 0,03 K till 0,17 K samt för dess fasutveckling och den synkroniserande effekten av yttre drivningar, 3) igenkännande av ett potenslagsformat spektrum S(f) ∝ f−α för den globala medeltemperaturen med α ∼ 0.8 mellan tidsskalor av flera decennier och El Nino -tidsskalor samt en mindre exponent i simulationer utan yttre drivning, 4)åtskiljning av aerosols egenskaper och klimateffekter i Indien på basen av plats och årstid, 5) en mera effektiv spridning av primära sulfataerosoler än sekundära kolaerosoler i simulationerna, 6) en ökning i monsunsnederbörden i Indien p.g.a. absorption av ljus av aerosoler och en sannolikt större minskning p.g.a. mattning av ljus av aerosoler och 7) en uppskattning på 0,19 K för den maximala kylningen p.g.a. större vulkanutbrott på höga och medelhöga breddgrader av det norra halvklotet. Resultaten kan vara nyttiga i isolering av klimatföränd-ringssignalen orsakad av människor, i noggrannare och mer detaljerade studier av processerna, i klimatprognoser med årtiondeskala, i värdering av modeller och som stöd för politisk beslutsfattning i samband med partikelutsläpp i Indien och andra länder

Ilmastonmuutoksen vaikutukset Suomessa metsänhoidon näkökulmasta

Kasvavat metsät sitovat hiiltä ilmakehästä, ja metsillä on siten tärkeä rooli ilmastonmuutoksen hillinnässä. Metsät ovat myös tärkeitä virkistysalueita, ja ennen kaikkea luonnontilaisia metsiä tarvitaan pyrittäessä suojelemaan luonnon monimuotoisuutta. Toisaalta metsäteollisuus on yksi Suomen tärkeimmistä teollisuudenaloista, joten myös metsien taloudellinen merkitys Suomessa on suuri. Ilmastonmuutoksen edetessä ja erilaisten metsien käyttöön liittyvien intressien ristipaineessa korostuu kysymys siitä, miten metsiä voidaan hyödyntää kestävällä tavalla. Metsänhoidon suositusten uudistamisen pohjaksi tarvitaan tietoja niin ilmastonmuutoksen suuruudesta kuin sen vaikutuksistakin. Tässä raportissa esitetään tämänhetkisen tietämyksen mukaiset arviot ilmastonmuutoksesta Suomessa sekä siitä, millaisia vaikutuksia muutoksella on Suomen metsiin ja metsätaloudelle. Viimeisten noin 150 vuoden aikana keskilämpötila on Suomessa jo kohonnut pari astetta. Tällä hetkellä lämpötila nousee Suomessa vajaat puoli astetta vuosikymmenessä. Kuluvan vuosisadan puoliväliin mennessä lämpötilan odotetaan kohoavan nykyisestä noin 1–1,5 astetta lisää. Kuinka paljon lämpötila nousee edelleen vuosisadan jälkipuoliskolla, riippuu suuresti kasvihuonekaasupäästöjen tulevasta maailmanlaajuisesta kehityksestä. Suomessa lämpötilan nousu on noin kaksi kertaa nopeampaa kuin maapallolla keskimäärin. Lämpenemisen lisäksi sateiden odotetaan lisääntyvän etenkin talvikuukausina. Toisaalta kesällä kuivuus voi vaivata aiempaa useammin. Lämpeneminen ja ilmakehän kohonnut hiilidioksidipitoisuus ovat jo omalta osaltaan kiihdyttäneet metsien kasvua, ja tulevaisuudessa metsiemme ennustetaan kasvavan yhä rivakammin. Toisaalta lisääntyvät metsätuhot voivat osittain neutralisoida tämän kehityksen. Erityisesti kuusikot ovat alttiita paitsi monille tuhonaiheuttajille, niin Etelä-Suomessa myös lisääntyvälle kuivuudelle. Tuhohyönteisistä lämpeneminen hyödyttää muun muassa kaarnakuoriaisiin lukeutuvaa kirjanpainajaa. Talvella roudan väheneminen vaikeuttaa puiden korjuuolosuhteita, mikä lisää juuristovaurioiden riskiä korjuun yhteydessä ja haittaa puunkorjuun logistiikkaa. Myös tuulituhojen riski kasvaa roudan vähentyessä. Kansainvälisesti tavoitteeksi on asetettu lämpenemisen rajaaminen maailmanlaajuisesti alle kahteen asteeseen esiteolliseen aikaan eli 1700-luvun puolivälin ilmastoon verrattuna. Tämä edellyttäisi nopeaa maailmanlaajuista kasvihuonekaasupäästöjen hillintää. Toistaiseksi kasvihuonekaasujen päästöjen kasvua ei ole pystytty rajoittamaan siinä määrin, että tavoitteen toteutuminen näyttäisi todennäköiseltä, joten on syytä varautua voimakkaampaan lämpenemiseen. Pahimman skenaarion toteutuessa lämpötila voi maailmanlaajuisesti kohota jopa yli neljä astetta kuluvan vuosisadan aikana. Yksittäisen metsänomistajan kannalta keskeistä on huolehtia metsien kasvusta ja elinvoimasta sekä pyrkiä myös tunnistamaan metsiä uhkaavat riskit, puuston ja maaston vaihtelevuus huomioon ottaen. Riskien hallinnan tueksi verkossa on saatavilla runsaasti avoimia ilmaston vaihteluita ja sään ääri-ilmiöiden esiintymistä kuvaavia tietoaineistoja sekä ennustepalveluita.Growing forests sequester carbon from the atmosphere, and hence forests have Aan important role in mitigating climate change. Forests are also important as recreational areas, and natural forests are needed in maintaining biodiversity. On the other hand, the economic importance of forests is substantial in Finland as the forest industry is a major contributor to wellbeing in the country. Ongoing climate change and the multiple contradictory interests towards forests expressed from different sectors in society make it important to study how forests can be exploited in a sustainable way. Information on the magnitude and impacts of climate change are needed in revising the forest management recommendations. In this report, we present an assessment of climate change in Finland based on current knowledge and describe the expected effects of the change on forests and forestry. Over the last 150 years, the mean temperature in Finland has already risen by about 2 °C. Presently, the temperature continues to increase with a rate of almost 0.5 °C per decade, and by the mid-century, temperatures in Finland are expected to be approximately 1–1.5 °C higher than at present. The rate of warming during the latter half of the 21st century will largely depend on the future evolution of global greenhouse gas emissions. In Finland, the rate of warming is about twice as large as the global average. In addition to warming, precipitation levels, particularly in winter, are expected to increase in the future. On the other hand, drought may occur in summer more frequently than at present. Increasing temperature and rising atmospheric carbon dioxide concentration have already contributed to accelerating forest growth. In the future, our forests are projected to grow even more rapidly. On the other hand, an increasing frequency of forest damages may partly overrule this development. Particularly, spruce forests are vulnerable to many insect pests but in southern Finland also to drought. An example of a pest benefitting from the warming is the European spruce bark beetle. In winter, reduction of soil frost complicates the logistics of forest harvesting and increases the risk of root damage during the harvest. The risk of wind damage also increases as the soil frost decreases. Internationally, the goal is to limit global warming to less than 2 °C compared to pre-industrial era, i.e., the mid-18th century. This would require rapid global mitigation of greenhouse gas emissions. So far, limiting the increase in global greenhouse gas emissions has not been adequately successful so that reaching the target would seem likely. Thus, there is a need to be prepared for a more severe warming. In the worst case, the temperature could rise even by more than 4 °C globally by the end of the 21st century. From the forest owner viewpoint, it is important to take care of the growth and vitality of the forest stands and to identify the risks threatening the stands, taking into account the variability of the stands and the terrain. To support risk management, there are available several open data sets on climate variability and the occurrence of extreme weather events, as well as forecasting services.Växande skogar binder kol från atmosfären och spelar därmed en viktig roll för att mildra klimatförändringarna. Skogar är också viktiga som rekreationsområden, och framför allt behövs naturskogar för att skydda den biologiska mångfalden. Å andra sidan är skogsindustrin en av Finlands viktigaste industribranscher och skogsbrukets ekonomiska betydelse är därmed också betydande. Pågående klimatförändringar, samt delvis till och med motstridiga intressen gentemot skogen som uttrycks från olika sektorer i samhället, gör det viktigt att studera hur skogen kan utnyttjas på ett hållbart sätt. Information om både omfattningen och konsekvenserna av klimatförändringarna behövs för att revidera skogsvårdsrekommendationerna. I denna rapport presenterar vi en bedömning av klimatförändringarna i Finland baserat på nuvarande information och beskriver de förväntade effekterna på skog och skogsbruk. Under de senaste 150 åren har medeltemperaturen i Finland redan stigit med cirka 2 °C. För närvarande stiger temperaturen i Finland med nästan 0,5 °C per årtionde. I mitten av 2000-talet förväntas temperaturerna vara cirka 1–1,5 °C högre än för närvarande. Uppvärmningshastigheten under den senare hälften av 2000-talet beror till stor del på den framtida utvecklingen av de globala utsläppen av växthusgaser. I Finland är uppvärmningen ungefär dubbelt så snabb som det globala genomsnittet. Förutom uppvärmningen förväntas nederbörden att öka i framtiden, särskilt på vintern. Å andra sidan kan torka förekomma på sommaren oftare än för nuförtiden. Högre temperaturer och stigande koldioxidkoncentration i atmosfären har redan bidragit till att förbättra skogstillväxten. I framtiden beräknas våra skogar växa ännu snabbare. Å andra sidan kan en ökande frekvens av skogsskador delvis radera denna utveckling. Det är särskilt granskogar som är sårbara för många skadedjur, men också för torka i södra Finland. Ett exempel på ett skadedjur som kan dra nytta av uppvärmningen är granbarkborren. På vintern komplicerar en minskning av tjäle logistiken för skogsavverkning och ökar risken för rotskador under avverkningen. Risken för vindskador ökar också när tjälen minskar. Internationellt har målet satts att begränsa den globala uppvärmningen till mindre än 2 °C jäm-fört med den förindustriella tiden, dvs mitten av 1700-talet. För att uppnå målet skulle det krävas en snabb minskning av de globala utsläppen av växthusgaser. Hittills har man inte lyckats begränsa ökningen av de globala utsläppen av växthusgaser i en sådan utsträckning att det skulle verka troligt att målet kan uppnås. Därför finns det ett behov av att förbereda sig för en större uppvärmning. I värsta fall kan den globala medeltemperaturen öka med mer än 4 °C till slutet av 2000-talet. Det är viktigt för den enskilda skogsägaren att ta hand om skogens tillväxt och livskraft, samt att försöka identifiera riskerna som hotar skogarna, med hänsyn till variationer i bestånd och terräng. För att stödja riskhanteringen finns det flera öppna datauppsättningar om klimatvariabilitet och förekomsten av extrema väderhändelser, såväl som prognostjänster

Climate change in the Baltic Sea region : a summary

Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins.Peer reviewe

Reconstructions of past climates from documentary and natural sources in Finland since the 18th century

In this paper both documentary and natural proxy data have been used to improve the accuracy of palaeoclimatic knowledge in Finland since the 18th century. Early meteorological observations from Turku (1748-1800) were analyzed first as a potential source of climate variability. The reliability of the calculated mean temperatures was evaluated by comparing them with those of contemporary temperature records from Stockholm, St. Petersburg and Uppsala. The resulting monthly, seasonal and yearly mean temperatures from 1748 to 1800 were compared with the present day mean values (1961-1990): the comparison suggests that the winters of the period 1749-1800 were 0.8 ºC colder than today, while the summers were 0.4 ºC warmer. Over the same period, springs were 0.9 ºC and autumns 0.1 ºC colder than today. Despite their uncertainties when compared with modern meteorological data, early temperature measurements offer direct and daily information about the weather for all months of the year, in contrast with other proxies. Secondly, early meteorological observations from Tornio (1737-1749) and Ylitornio (1792-1838) were used to study the temporal behaviour of the climate-tree growth relationship during the past three centuries in northern Finland. Analyses showed that the correlations between ring widths and mid-summer (July) temperatures did not vary significantly as a function of time. Early (June) and late summer (August) mean temperatures were secondary to mid-summer temperatures in controlling the radial growth. According the dataset used, there was no clear signature of temporally reduced sensitivity of Scots pine ring widths to mid-summer temperatures over the periods of early and modern meteorological observations. Thirdly, plant phenological data with tree-rings from south-west Finland since 1750 were examined as a palaeoclimate indicator. The information from the fragmentary, partly overlapping, partly nonsystematically biased plant phenological records of 14 different phenomena were combined into one continuous time series of phenological indices. The indices were found to be reliable indicators of the February to June temperature variations. In contrast, there was no correlation between the phenological indices and the precipitation data. Moreover, the correlations between the studied tree-rings and spring temperatures varied as a function of time and hence, their use in palaeoclimate reconstruction is questionable. The use of present tree-ring datasets for palaeoclimate purposes may become possible after the application of more sophisticated calibration methods. Climate variability since the 18th century is perhaps best seen in the fourth paper study of the multiproxy spring temperature reconstruction of south-west Finland. With the help of transfer functions, an attempt has been made to utilize both documentary and natural proxies. The reconstruction was verified with statistics showing a high degree of validity between the reconstructed and observed temperatures. According to the proxies and modern meteorological observations from Turku, springs have become warmer and have featured a warming trend since around the 1850s. Over the period of 1750 to around 1850, springs featured larger multidecadal low-frequency variability, as well as a smaller range of annual temperature variations. The coldest springtimes occurred around the 1840s and 1850s and the first decade of the 19th century. Particularly warm periods occurred in the 1760s, 1790s, 1820s, 1930s, 1970s and from 1987 onwards, although in this period cold springs occurred, such as the springs of 1994 and 1996. On the basis of the available material, long-term temperature changes have been related to changes in the atmospheric circulation, such as the North Atlantic Oscillation (February-June).Paleoklimatologia tutkii ilmaston yleistä luonnetta maapallolla ja sen eri alueilla ajalta ennen nykyisenlaisia meteorologisia mittaushavaintoja. Suomessa pisin yhtenäinen ilmastomittausten sarja on Helsingistä vuodesta 1828 lähtien. Mikäli haluamme tietää maamme ilmaston vaihteluista tätä varhaisemmalta ajalta, on otettava käyttöön epäsuorat aineistot eli ns. proksiaineistot. Niitä on mitä erilaisimpia, joita edustavat mm. varhaiset ilmastomittaukset, puiden kasvun vaihtelua kuvastavat lustokalenterit, järvisedimentit sekä muistiinpanot jokien jäänlähdöistä sekä koivun lehteentulosta. Tässä tutkimuksessa on keskitytty maamme ilmaston kehityksen ymmärtämiseen 1700-luvulta lähtien käyttäen apuna niin historian arkistoista kuin luonnonarkistoista koottuja proksiaineistoja. Ensimmäisessä osatutkimuksessa käsiteltiin varhaisia ilmastomittauksia, joita ryhdyttiin kirjaamaan Suomessa muistiin 1730-luvulta lähtien. Maamme pisin ja luotettavimmin dokumentoitu varhainen ilmastollinen havaintosarja on Turusta, missä Turun Akatemian professorit organisoivat suhteellisen säännöllisen havaintojenteon aina 1740-luvulta 1820-luvulle. Vaikka päiväkirjojen tiedot mittalaitteiden sijoittamisesta, täsmällisistä havaintopaikoista ja havaintoperusteista ovat usein puutteelliset, ne tarjoavat päivittäistä tietoa säästä ympäri vuoden, mihin muut proksiaineistot eivät yllä. Varhaisten ilmastomittausten analyysia jatkettiin toisessa osatutkimuksessa Ylitornion ja Tornion varhaisten havaintosarjojen avulla. Näistä sarjoista koostettuja lämpötilasarjoja käytettiin puunlustojen paksuuskasvun vaihteluiden selvittämisessä viimeisten kolmen vuosisadan aikana. Havaittiin, että puunlustojen kasvu Pohjois-Suomessa oli riippuvainen keskikesän (heinäkuun) lämpötilasta. Tutkimuksessa todettiin myös, ettei Lapin puunlustojen paksuuskasvun ja heinäkuun lämpötilojen välisessä yhteydessä eli sensitiivisyydessä ole tapahtunut merkittävää vähenemistä kuluneen kolmen sadan vuoden aikana. Tulos on mielenkiintoinen, sillä aikaisemmin oli raportoitu sensitiivisyyden vähentyneen puunkasvun ja lämpötilan välillä pohjoisilla leveysasteilla viimeisen 50 vuoden aikana. Kolmannessa osatutkimuksessa kehitettiin metodia hajanaisten fenologisten havaintosarjojen koostamiseksi yhtenäiseksi aikasarjaksi Lounais-Suomen osalta. 1750-luvun puolenvälin jälkeen muistiin kirjatuilla fenologisilla havainnoilla on yksi suuri puute - tavallisesti sarjat ovat 2-10 vuoden pituisia kultakin paikkakunnalta. Sarjoista tutkittiin aluksi niiden sensitiivisyyttä lämpötilaa ja sateisuutta kohtaan ja havaittiin selvä positiivinen yhteys lämpötilan osalta. Tämän jälkeen erillisistä fenologisista havaintosarjoista koostettiin yhtenäinen kokonaisfenologia-indeksisarja. Aikasarjan avulla tutkittiin sarjan sensitiivisyyttä lämpötilaan ja havaittiin selvä positiivinen yhteys helmi-kesäkuun keskilämpötiloihin. Näin ollen kokonaisfenologiaindeksisarja soveltuu lämpötilarekonstruktiota varten. Tutkimuksessa oli mukana myös puunlustoaineistoja, joista havaittiin ajan suhteen muuttuva riippuvuus helmi-kesäkuun lämpötiloihin. Neljäs osatutkimus käsitteli kevään lämpötilojen kehitystä Lounais-Suomessa vuodesta 1750 lähtien. Kun viimeisten 150 vuoden aikana on tapahtunut maassamme vuosikeskilämpötilojen ja erityisesti keväiden keskilämpötilojen nousua, oli mielenkiintoista tietää, millaisia keväiden lämpöolot olivat tätä edeltävällä ajalla? Työssä rakennettiin malli, johon sisältyi niin historiallisia lähteitä, kuten Aurajoen jäänlähtötietoja, tietoja Itämeren vuotuisen jääpeitealan vaihteluista, edellisen osatutkimuksen kokonaisfenologiaindeksisarja kuin järvisedimenttiaineisto sekä moderneja ilmastomittauksia, joita edusti Turun kuukausikeskilämpötila-aineisto. Kyseinen lämpötilarekonstruktio selitti 66 % havaituista lämpötilanvaihteluista tarkasteltuna ajanjaksona. Koostetun aikasarjan avulla tutkittiin keväiden keskilämpötiloja ja havaittiin, että viimeisen 250 vuoden aikana on ollut sekä kylmempiä että lämpimämpiä vaiheita. Kylmimmät vaiheet ajoittuvat 1850-luvun molemmin puolin, 1810-luvun seutuville sekä 1780-luvulle. Lämpimimmät keväät ovat esiintyneet vuodesta 1987 lähtien, 1930-luvulla sekä 1820-luvulla. Samoin tutkittiin vaihteluiden taustalla vaikuttavia tekijöitä ja niiden merkitystä kevätlämpötilojen vaihteluissa. Havaittiin, että kevätlämpötiloilla on positiivinen ja ajan suhteen suhteellisen vakaa yhteys Pohjois-Atlantin heilahduksen vaiheisiin

Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective

The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a "PEEX region". It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land-atmosphere-ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate-Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially "the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change" and the "socio-economic development to tackle air quality issues".Peer reviewe

Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective

The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a “PEEX region”. It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially “the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change” and the “socio-economic development to tackle air quality issues”

Pan-Arctic seasonal cycles and long-term trends of aerosol properties from ten observatories

Even though the Arctic is remote, aerosol properties observed there are strongly influenced by anthropogenic emissions from outside the Arctic. This is particularly true for the so-called Arctic haze season (January through April). In summer (June through September), when atmospheric transport patterns change, and precipitation is more frequent, local Arctic, i.e. natural sources of aerosols and precursors, play an important role. Over the last decades, significant reductions in anthropogenic emissions have taken place. At the same time a large body of literature shows evidence that the Arctic is undergoing fundamental environmental changes due to climate forcing, leading to enhanced emissions by natural processes that may impact aerosol properties. In this study, we analyze nine aerosol chemical species and four particle optical properties from ten Arctic observatories (Alert, Gruvebadet, Kevo, Pallas, Summit, Thule, Tiksi, Barrow, Villum, Zeppelin) to understand changes in anthropogenic and natural aerosol contributions. Variables include equivalent black carbon, particulate sulfate, nitrate, ammonium, methanesulfonic acid, sodium, iron, calcium and potassium, as well as scattering and absorption coefficients, single scattering albedo and scattering Ångström exponent. First, annual cycles are investigated, which despite anthropogenic emission reductions still show the Arctic haze phenomenon. Second, long-term trends are studied using the Mann-Kendall Theil-Sen slope method. We find in total 28 significant trends over full station records, i.e. spanning more than a decade, compared to 17 significant decadal trends. The majority of significantly declining trends is from anthropogenic tracers and occurred during the haze period, driven by emission changes between 1990 and 2000. For the summer period, no uniform picture of trends has emerged. Twenty-one percent of trends, i.e. eleven out of 57, are significant, and of those five are positive and six are negative. Negative trends include not only anthropogenic tracers such as equivalent black carbon at Kevo, but also natural indicators such as methanesulfonic acid and non-sea salt calcium at Alert. Positive trends are observed for sulfate at Zeppelin and Gruvebadet. No clear evidence of a significant change in the natural aerosol contribution can be observed yet. However, testing the sensitivity of the Mann-Kendall Theil-Sen method, we find that monotonic changes of around 5 % per year in an aerosol property are needed to detect a significant trend within one decade. This highlights that long-term efforts well beyond a decade are needed to capture smaller changes. It is particularly important to understand the ongoing natural changes in the Arctic, where interannual variability can be high, such as with forest fire emissions and their influence on the aerosol population. To investigate the climate-change induced influence on the aerosol population and the resulting climate feedback, long-term observations of tracers more specific to natural sources are needed, as well as of particle microphysical properties such as size distributions, which can be used to identify changes in particle populations which are not well captured by mass-oriented methods such as bulk chemical composition

State of the climate in 2013

In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Niña or El Niño events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earths surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series. © 2014, American Meteorological Society. All rights reserved