La temperatura malata del nostro pianeta

La temperatura malata del nostro pianeta

Il cambiamento climatico è una tematica che non cattura ancora l’opinione pubblica come dovrebbe. Una ragione è che le fluttuazioni termiche annue, a scala globale, sono molto più piccole delle variazioni diurne a piccoal scala, o di quelle stagionali a scala locale o globale. Tuttavia, si può notare un certo parallelismo tra la temperatura corporea di una persona e il clima. Se uno monitorasse la propria temperatura corporea in ogni minuto del giorno, noterebbe alcune variazioni diurne di poco meno di 1 °C. Inoltre, persone diverse possono avere temperature corporee diverse, anche in questo caso con variazioni di 1 °C o più, anche in funzione delle proprie condizioni personali. Un atleta, immediatamente dopo una gara, o una persona normale dopo un esercizio stressante, possono avere una temperatura corporea superiore anche di 1 °C rispetto alla norma. Bene, queste variazioni normali rappresentano il “tempo meteorologico” di una persona, e non indicano necessariamente la presenza di qualche malattia.

Tuttavia, se la temperatura di qualcuno inizia ad aumentare, più o meno regolarmente, nel tempo, questa variazione rappresenta una sorta di “clima” di una persona, che sta cambiando, e può essere il sintomo di qualcosa non necessariamente positivo per la salute della persona. Questo è vero anche se queste variazioni “climatiche” sono inferiori a quelle che in precedenza abbiamo chiamato variazioni del “tempo meteorologico”. Il problema scientifico è quindi distinguere le variazioni normali da quelle anormali, differenziandone le scale. Mentre il problema comunicativo è come informare l’opinione pubblica, in modo corretto ma comprensibile, riguardo a queste dinamiche.

Abbiamo la fortuna di avere a disposizione oltre un secolo di osservazioni meteorologiche, eseguite in diverse stazioni dislocate in varie località della Terra. Molti centi climatici hanno raccolto dei sottoinsiemi di questi dati e li hanno analizati, in maniera da eliminare i trend o i dati anomali. E hanno calcolato una stima della temperatura media globale. Poiché la scelta delle stazioni ed il trattamento dei dati è stato differente da centro a centro, ci sono alcune differenze tra i vari dataset, anche se il segnale che emerge è abbastanza univoco e incontestabile: la temperatura media globale sta aumentando.

Inoltre, diversi modelli climatici (ora si chiamano più propriamente Earth System Models, cioè modelli del sistema terrestre) sono stati fatti girare da vari gruppi di ricerca per simulare il clima terrestre futuro. Anche se ogni modello tende a fornire una risposta particolare, oggi si preferisce guardare a questo tipo di proiezioni considerando l’insieme de irisultati di un ampio gruppo di modelli. Questo è stato fatto, ad esempio, nel corso dell’esperimento CMIP5, i cui risultati preliminari hanno costituito il nucleo delle affermazioni riportate sull’ultimo rapporto IPCC.

Con Stefano Caserini, coordinatore di climalteranti.it, abbiamo avuto l’idea di combinare le due informazioni, dati e proiezioni modellistiche, in modo visuale. Abbiamo scelto come dataset quello del GISS, e come dati modellistici gli insiemi dell’esperimento CMIP5, selezionando tre diversi scenari: RCP 2.6, RCP 4.5 e il più estremo RCP 8.5, corrispondenti rispettivamente ad emissioni basse, medie e alte. In particolare, lo scenario RCP 8.5 corrisponde a quello che ci si aspetteremmo che succedesse nel caso in cui le emissioni proseguissero a variare come hanno fatto finora (cioè con un continuo incremento):

Monthly climate change - GISS + RCP 8.5

Evolution of monthly mean temperature anomalies from 1880 to 2100, referred to the period 1880-1909. the observations relative to the period January 1880 – April 2016 are extraxted from dataset GISS, while the simulation data, relative to the period 2017-2100, have been gathered from the ensemble values of experiment CMIP5, in this case selecting the extreme high-emissions scenario RCP 8.5.

Qui vediamo invece la situazione che ci aspettiamo secondo lo scenario “migliore”: RCP 2.6:

Monthly climate change - GISS + RCP 2.6

Evolution of monthly mean temperature anomalies from 1880 to 2100, referred to the period 1880-1909. the observations relative to the period January 1880 – April 2016 are extraxted from dataset GISS, while the simulation data, relative to the period 2017-2100, have been gathered from the ensemble values of experiment CMIP5, in this case selecting the low-emissions scenario RCP 2.6.

mentre qui è presentato qullo intermedio RCP 4.5:

Monthly climate change - GISS + RCP 4.5

Evolution of monthly mean temperature anomalies from 1880 to 2100, referred to the period 1880-1909. the observations relative to the period January 1880 – April 2016 are extraxted from dataset GISS, while the simulation data, relative to the period 2017-2100, have been gathered from the ensemble values of experiment CMIP5, in this case selecting one of the intermediate scenarios, i.e. the medium-emissions RCP 4.5 .

Le simulazioni modellistiche sono disponibili nel periodo 1860-2100, mentre le osservazioni GISS si riferiscono al periodo 1880-2016 (l’ultimo dato è quello di aprile). Ho integrato i due dataset calcolando per ognuno la rispettiva anomalia (differenza rispetto alla media) nel periodo comune 1880-1909 (un trentennio, come di solito si fa nelle analisi climatiche).

La visualizzazione del risultato l’ho fatta in due modi diversi. Ho usato il metodo a spirale delle anomalie mensili, sviluppato orinariamente da Ed Hawkins per i dati HadCRUT, ed ho anche mostrato un grafico lineare delle anomalie mensili, come avevo fatto in un post recente per visualizzare i dati HadCRUT. Il primo dei due metodi è visualizzato in dettaglio in questo post su climalteranti.it, per cui qui di seguito descriverò il secondo e farò alcune brevi considerazioni generali (brevi perché ritengo che i grafici parlino da soli).

Si tratta di due metodi diversi ma efficaci per visualizzare il cambiamento climatico in corso e quello che ci attende. Le animazioni iniziano dal 1880 e, mese per mese, mostrano le variazioni di temperatura fino ad aprile 2016. Si vede bene il raffreddamento nel primo decennio del 1900, il riscaldamento tra il 1920 e il 1930, la stazionarietà nel decennio della seconda guerra mondiale, il successivo piccolo riscaldamento, la nuova stasi tra il 1960 ed il 1970, e poi il rapido incremento del rateo di riscaldamento a partire dal 1980, con gli ultimi quindici anni in grado di aggiornare almeno un record mensile praticamente ogni anno. Fino ad arrivare al periodo anomalo degli

ultimi nove mesi, che si colloca totalmente al di fuori dal range dei valori precedenti.

Le simulazioni climatiche future degli scenari CMIP5 mostrano un continuo riscaldamento, praticamente analogo per i tre scenari fino al 2030, dopodiche gli scenari si differenziano nettamente tra loro. Notiamo anche che il rateo di riscaldamento fornito dai modelli è più regolare, grazie al fatto che questi dati sono rappresentativi di un insieme e non il risultato di un modello singolo. I valori anomali registrati nel quadrimentre gennaio-aprile 2016 sembrano rientrare nelle medie intorno al 2025-2030, quando saranno rappresentativi del “clima normale” di quegli anni.

Dopo il 2030, come si diceva, gli scenari si differenziano rapidamente, con l’unico risultato comune di un riscaldamento più sensibile d’inverno. A fine secolo, anche secondo lo scenario di basse emissioni (RCP 2.6), una stagione come l’ultima trascorsa apparirà come un periodo freddo. Ma, se si guarda lo scenario più estremo (RCP 8.5, che corrisponde alle emissioni alte), apparirà quasi come una sorta di mini-era glaciale…

Gli scenari iniziano a differenziarsi intorno al 2030… c’è ancora un briciolo di tempo per cercare di far verificare lo scenario sopportabile RCP 2.6 invece di quello estremo RCP 8.5… non tanto tempo, perchè i gas serra aumentano inesorabilmente, e il conseguente riscaldamento globale anche.

Possiamo scegliere… dobbiamo scegliere!

Annunci

An epochal-symbolic threshold: the CO2 concentration at Mauna Loa has exceeded 400 ppm!

It was in the air for days, and it has also created a certain expectation, with trepidation. Similarly as when we are awaiting the outcome of a surgery for a family member. But this event has nothing to rejoice. The question is very simple. At the Mauna Loa observatory, CO2 values ​​whose average over an entire day was greater than 400 ppm were recorded. One ppm means one part per million. That is to say, on a million of air molecules, 400 are CO2. It seems a small and harmless number. But it is not, unfortunately. Because these small quantities of gas are those that regulate the greenhouse effect on our planet. The greenhouse effect on Earth is responsible for the fact that the average global temperature, instead of being equal to a chilling value of -18°C, is approximately 15°C, a value much more livable for our species. And this happens thanks to the presence of a number of components, in the terrestrial atmosphere, which leave no escape throughout the infrared radiation that the Earth emits, but retain a certain part. It is a positive effect, then. More greenhouse gases there are in the Earth-atmosphere system, the more the greenhouse effect is big. Variations are small, almost imperceptible, few tenths of a degree, but accumulated can lead to large variations.

The greenhouse effect in short.

The greenhouse effect in short.

Few words on Mauna Loa observatory. Where is it? Here, on Hawaii islands.

An image of Mauna Loa Observatory.

An image of Mauna Loa Observatory.

Erected in 1956, the first CO2 measurements date 1958, thus it is the most ancient observatory measuring CO2 on Earth. Somebody criticizes the choice of the site as nearby there is the Kilauea volcano, whose emissions may affect the measurements. However, the observatory altitude is 3397m, and its elevation and location (in the middle of the Pacific ocean, away from major air pollution sources) make this site as an ideal place to sample the atmosphere. The high elevation of the observatory keeps also far away the lower local pollutants emitted below the observatory (such as also volcanic emissions), due to fact that it is quite higher than the strong marine temperature inversion layer present for most of the time in the region. An “a posteriori” demonstration of the quality of these data is the comparison of the CO2 trend of the Mauna Loa data (1.64 ppm per year) with the global trend (1.66 ppm per year), calculated considering the average of all remote stations in the world: they are statistically indistinguishable.

Global atmospheric CO2 (NOAA) versus Mauna Loa CO2 (NOAA). Credits: Skeptical Science.

Global atmospheric CO2 (NOAA) versus Mauna Loa CO2 (NOAA). Credits: Skeptical Science.

Let’s now came back to the original point. Yesterday, daily mean CO2 concentration has exceeded 400 ppm. It did not happen for about 3 million years. That means this has never happened since man lives on Earth. 400 ppm is a symbolic epochal threshold for the humanity..

The news is not yet official but, after the graph produced by NOAA (National Oceanic Atmospheric Administration), here reported (that on the link is regularly updated), the U.S. federal agency that deals with climate, the CBS has released yesterday a service confirming the measure.

Last year daily and weekly CO2 concentrations at Mauna Loa.

Last year daily and weekly CO2 concentrations at Mauna Loa.

It must be emphasized, once again, that the carbon dioxide enters the atmosphere as a result of the human use (and abuse) of fossil fuels: oil, gas, coal, methane, etc. Since we have started to use them (which means, since the Industrial Revolution, or even better, since the invention of the Watt machine), the history and prehistory of the human race have been accompanied by a carbon dioxide concentration lower than 300 ppm.

A preserved Watt beam engine at Loughborough University. Credits: wikipedia.

A preserved Watt beam engine at Loughborough University. Credits: Ashley Dace.

Still in the middle of the eighteenth century, it was equal to 280 ppm. Then, it started its apparently unstoppable growth till the actual values of 400 ppm.

CO2 in last 1200 years. Credits: IPCC AR4.

CO2 in last 1200 years. Credits: IPCC AR4.

Carbon dioxide, as well known, is the main greenhouse gas (GG). I like the description of the greenhouse effect given in this Italian blog: GGs trap the sun’s heat in the atmosphere, as a duvet traps heat in our body when we are in our bed during the winter. If there were no greenhouse gases, it would be like to sleep without duvet. But having too abundant greenhouse gas is like sleeping with two duvets. Nightmares and sweat are guaranteed…

We said that our Earth experienced for the last time an atmospheric concentration of carbon dioxide of 400 ppm about three millions years ago, i.e. before the appearance of the so-called Homo sapiens. At that time, the temperatures were 3-4°C higher than now, and the sea level was about 25 meters higher than now.

Reconstruction of the atmospheric concentration of CO2 in the last 65 million years: in the distant geological past, there have been periods when this greenhouse gas was vastly more abundant than today. For example, between the Paleocene and Eocene, around 50 to 55 million of years ago, it was about 2000 ppm. But this comparison cannot reassure about the current situation. At that time, indeed, the planet was completely different, with a different geology, climate and environment, and even some prehistoric human species existed. But today we live in a world more and more overcrowded, short of natural resources and plagued by numerous criticalnesses (environmental, demographic, social, economic and alimentary) that make humanity fragile in the face of abrupt climate change. During the Pliocene (between about 3 and 5 million years ago, red line), for the last time before today, a CO2 concentrations next to 400, sometimes 500 ppm was reached. Source: alpineanalytics.

Reconstruction of the atmospheric concentration of CO2 in the last 65 million years: in the distant geological past, there have been periods when this greenhouse gas was vastly more abundant than today. For example, between the Paleocene and Eocene, around 50 to 55 million of years ago, it was about 2000 ppm. But this comparison cannot reassure about the current situation. At that time, indeed, the planet was completely different, with a different geology, climate and environment, and even some prehistoric human species existed. But today we live in a world more and more overcrowded, short of natural resources and plagued by numerous criticalnesses (environmental, demographic, social, economic and alimentary) that make humanity fragile in the face of abrupt climate change. During the Pliocene (between about 3 and 5 million years ago, red line), for the last time before today, a CO2 concentrations next to 400, sometimes 500 ppm was reached. Source: alpineanalytics.com.

Reconstruction of the atmospheric concentration of CO2 in the last 65 million years: in the distant geological past, there have been periods when this greenhouse gas was vastly more abundant than today. For example, between the Paleocene and Eocene, around 50 to 55 million of years ago, it was about 2000 ppm. But this comparison cannot reassure about the current situation. At that time, indeed, the planet was completely different, with a different geology, climate and environment, and even some prehistoric human species existed. But today we live in a world more and more overcrowded, short of natural resources and plagued by numerous criticalnesses (environmental, demographic, social, economic and alimentary) that make humanity fragile in the face of abrupt climate change. During the Pliocene (between about 3 and 5 million years ago, red line), for the last time before today, a CO2 concentrations next to 400, sometimes 500 ppm was reached. Source: alpineanalytics.

Usually, CO2 concentration shows a marked annual cycle, due to the effect of the vegetation respiration: for this reason, the cycle is much more evident in the midlatitudes of the northern hemisphere, where the vegetation covers more extensively the Earth surface. Normally, during the first half of May, the carbon dioxide reaches the “peak” year: the concentration decreases after the forests of the northern hemisphere have completed the foliation. Thus, this year the epochal peak of 400 ppm has been exceeded almost at the end of the increasing period, and soon the mean value will come back below 400 ppm. But, year after year, the peak always grows.

A rough graphic simulation carried out by myself using the monthly (monthly, not daily: this is way the value is significantly lower than 400 ppm!) data measured at Mauna Loa (I have just graphically repeated the last year trend; yes, I know, very rough, but it gives the idea) shows that we have still two years in which we could see some values with daily or monthly values lower than 400 ppm. Then, after 2016, we will enter in a new era: the above 400 ppm CO2 era.

Monthly mean carbon dioxide concentrations measured at Mauna Loa (until April 2013) and hypothized for the next three years by continuing the last year trend. It is evident as September and October 2014 risk to be the last months with a CO2 monthly mean value below 400 ppm.

Monthly mean carbon dioxide concentrations measured at Mauna Loa (until April 2013) and hypothized for the next three years by continuing the last year trend. It is evident as September and October 2014 risk to be the last months with a CO2 monthly mean value below 400 ppm.

Monthly mean carbon dioxide concentrations measured at Mauna Loa (until April 2013) and hypothized for the next three years by continuing the last year trend. It is evident as September and October 2014 risk to be the last months with a CO2 monthly mean value below 400 ppm.

If you do not trust my rough projection, you may enjoy in watching this video, that shows the time history of atmospheric carbon dioxide from 800,000 years before present until January, 2012 (and it is possible to imagine how it will continue).

By the way, the video shows that, at high latitudes, the 400 ppm threshold has already been exceeded in some months several years ago. But here we are talking about Mauna Loa, Hawaii: which is located in an equatorial area and is representative of the world mean (remember the first figure).

And, as now people “old” like me is surprised by thinking that the first year university students had never experienced a world without mobile phone (and few year later we may repeat the same discussion for smartphones, facebook, twitter, …), some years later the young generation will be born in an above-400-ppm-CO2-era.

The effects of increased concentrations of greenhouse gases are not immediately evident. Until now, the planet’s average temperatures has increased only by 0.8°C with respect to before the Industrial Revolution, but already many people complain that no longer exist transition seasons and seasons are no longer those known in the past. The following video from NASA summarizes in 30 seconds how world temperatures have changed in the past 120 years.

The climate destabilization triggered by greenhouse gases that humans have released into the atmosphere also manifest in the increase of extreme weather events: heat or cold waves, drought and floods.

The cold spring in western Europe and a big portion of US, for example, is probably a side effect of the massive melting of Arctic ice which took place last summer. While talking of spring temperatures, let’s give a look on a global map. Here it is shown the map referring to the first two months of 2013 spring (we remember here that meteorologists count seasons starting from the first day of the month, so spring means March, April and May). I have decided to underline these data, as I am reading a lot of nonsense related to actual weather. The map reveals that there are some areas characterized by dark blue, which means cold. These areas (Canada, US and Europe) are densely populated by industrialized humans. There are also several areas characterized by quite large warm anomalies, but they concern some underpopulated, or not populated at all, areas of the planet. This is why we heard only about cold, and nothing about warm. We care only about what happens where we live. But climate do not make such distinctions, and from a climatological point of view, US and Antarctica are equal!

Anomaly of surface temperatures recorded during March and April, 2013, with respect to the period 1981-2010. A large cold area covers a big portion of North America and another one covers most of Europe, while central Asia, Africa, Greenland and both polar regions are experiencing unusually warm periods. Source: NCEP-NCAR.

Anomaly of surface temperatures recorded during March and April, 2013, with respect to the period 1981-2010. A large cold area covers a big portion of North America and another one covers most of Europe, while central Asia, Africa, Greenland and both polar regions are experiencing unusually warm periods. Source: NCEP-NCAR.

The temperature anomalies appear to be strongly connected with the corresponding anomalies of the geopotential pattern at 500 hPa.

Anomaly of 500 hPa geopotential height recorded during March and April, 2013, with respect to the period 1981-2010. Note the almost perfect coincidence between cold areas and areas with negative 500 hPa anomaly. Source: NCEP-NCAR.

Anomaly of 500 hPa geopotential height recorded during March and April, 2013, with respect to the period 1981-2010. Note the almost perfect coincidence between cold areas and areas with negative 500 hPa anomaly. Source: NCEP-NCAR.

A short look on the sea surface temperatures (SST) in the North Pole area reveals as there is a relevant positive anomaly of SST in the zone of the North Pole, which experienced on last September the largest ice-free extension. And it is impossible to think that these phenomena are not connected…

Anomaly of SST recorded during March and April, 2013, with respect to the period 1981-2010. Note the almost perfect coincidence between cold areas and areas with negative 500 hPa anomaly. Source: NCEP-NCAR.

Anomaly of SST recorded during March and April, 2013, with respect to the period 1981-2010. Note the almost perfect coincidence between cold areas and areas with negative 500 hPa anomaly. Source: NCEP-NCAR.

2012 global temperatures: still in medal zone!

2012 global temperatures: still in medal zone!

Another year has already passed. So let us comment what happened in 2012, initially at global scale and then zooming on Europe and on Italy. As usual, while we wait for the official data that will be published in the next two – three months from institutional sites (CRU, GISS, NASA, etc. – the detailed list can be found on last year’s post), the fastest method is to use the database NOAA/NCEP (in particular, I have used this site with monthly composites). I remember that these are not raw but processed data: in particular, they are averaged on a grid of 2.5 degrees in longitude and latitude, which is equivalent, at our latitudes, to a square of about 300 x 300 km2. It is therefore impossible to make local considerations using this type of data.

Surface temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.

Surface temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.

The annual mean anomaly (note that the graphs in this post, unless otherwise stated, are all referred to the thirty years 1981-2010, which is the most recent period, to account for the warming occurred in the last three decades) shows a positive mean value, with the highest values in the Arctic and Antarctic polar regions, over Canada and the United States, and a narrow strip of territory stretching from the Mediterranean to Siberia. The most evident negative anomalies are concentrated in three small areas (Alaska, Mongolia and a portion of the Antarctic coast). For the rest, the anomalies remain (in absolute) below 1°C, and are prevailingly positive in the northern hemisphere over south-central Europe and North America, and negative in part of Asia and Northwestern Europe, while in the southern hemisphere, excluding Antarctica, show a less clear signal.

Globally, the mean anomaly was 0.26 °C, i.e. 0.07 °C higher than that of 2011, equal to 0.19 °C. This value is in fifth place in the scale of thermal values calculated using the NOAA-NCEP data, 0.09 °C away from year 2005, which leads the list. In football jargon, we would say that 2012 has earned Europe League qualification. In absolute terms, however, the integral data on the grid points (weighted by their respective surface, of course) is 14.30 °C. This numerical value, however, should be corrected to make it compatible with the values of other datasets. I will shorthly explain here how. Referring to the data (Table and figure below), we can see how the data NOAA-NCEP result, on average, underestimated by about 0.35 °C. I underline here that, concerning the data GISS, CRU and NCDC, both in the table and in the figure, for the year 2012, the average values referred to the period December 2011 – November 2012, instead of the annual average, not yet available, have been used (however, looking at the values of the past years, the difference, in general, is not higher than 0.02 ° C).

Annual mean values and anomalies for the three major databases, in comparison with the values calculated by the database grid points NOAA-NCEP used in this post. 2012 mean values, for the databases CRU, GISS and NCDC, refer to the period December 2011 - November 2012 and are shown in italics. The last column shows the NOAA-NCEP values "corrected" by adding the average difference in the 1981-2010 thirty years between the average of the other three databases and the average NOAA-NCEP, equal to 0.35 °C.

Annual mean values and anomalies for the three major databases, in comparison with the values calculated by the database grid points NOAA-NCEP used in this post. 2012 mean values, for the databases CRU, GISS and NCDC, refer to the period December 2011 – November 2012 and are shown in italics. The last column shows the NOAA-NCEP values “corrected” by adding the average difference in the 1981-2010 thirty years between the average of the other three databases and the average NOAA-NCEP, equal to 0.35 °C.

Let us note here that, in the past year, the CRU database has been slightly modified (see for example here), so some numerical values may slightly differ from previous assessments. In any case, the comparison reveals that, more or less, all databases are in agreement on the measurements and show the 2012 as warmer than the average of the most recent thirty years. On the other hand, the first year colder than period 1981-2010, for three databases on four, is the 2000 …, while to find the first year colder than period 1981-2010 for all four databases, it is necessary to go back to 1996!

Annual average values for the three major databases, in comparison with the gridded values calculated by the database NOAA-NCEP used in this post.

Annual average values for the three major databases, in comparison with the gridded values calculated by the database NOAA-NCEP used in this post.

However, beside the classifications, which can not be devoided by errors (observational, of average, station selection, interpolation, etc..), it is interesting to see how, if we take the ten-year period 2003-2012, it contains eight of the ten warmest years.

The signal is not present only at the surface: in fact, the map at 500 hPa (level corresponding to about 5500 m a.s.l., i.e. in the middle of the troposphere) shows values a bit smaller but still of the same sign, indicating that the warming occurred in the whole troposphere and not only of the surface stations (or of the boundary layer).

500 hPa temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.

500 hPa temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.

Let us go now to examine the graphs related to individual seasons. The winter 2011-2012, which includes December 2011, shows a strong warming on the Arctic regions, with maximum values between Svalbards and Siberia larger than 16 °C, but is also great on Canada and the United States, while practically all the Central Asia (from Caspian Sea to Korea), West Africa and the areas around the Bering Strait show anomalies of -4/-5°C. Unlike the Arctic, however, Antarctica shows less significant and more varied values, and also part of Greenland has recorded temperatures below average.

Surface temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.Surface temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.

Surface temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.Surface temperature anomaly (°C) in 2012 with respect to the reference period 1981-2010. Data NOAA-NCEP.

Concerning the spring 2012, different warm areas are noticeable on the Antarctic mainland, while in the Arctic only the area above the Eurasia maintains strongly positive anomalies, in both cases with values of 6°C or more. Other hot spots are the United States and much of Europe, as well as north-western Asia and part of Greenland. Areas with strong negative anomaly practically do not exist, except for part of Alaska and a portion of Antarctic coasts.

Surface temperature anomaly (°C) on the period March - May 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period March – May 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Summer 2012 is the season with the more moderated extreme anomalies. Almost the entire northern hemisphere has the land warmer than average, with rare exceptions (Great Britain and Scandinavia in Europe, and a small Siberian region over Mongolia in Asia), while in the southern hemisphere the oceans show more positive anomalies, and negative ones are present in the western parts of South America and Africa, and Australia. The most negative anomalies, however, are recorded on the Antarctic coastal areas, with values lower than -3°C, while inside there is the largest positive anomaly (more than 4°C).

Surface temperature anomaly (°C) on the period June - August 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period June – August 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

The fall 2012 shows a configuration with distinctly positive anomalies on Arctic areas (with maximum larger than 8°C and peaks of 10°C) and still positive on part of the continents in the northern hemisphere (except the region between Alaska and Canada and Central Asia) and Antarctica (with the exception of the Antarctic Peninsula and neighbour sea, which show the minima anomaly, lower than -4°C). In the southern hemisphere, there are some spots with slightly positive anomaly.

Surface temperature anomaly (°C) on the period September - November 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period September – November 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

For completeness, we show also the image for the month of December 2012, which completes the analysis of the year, as the distribution of anomalies is singular. Obviously, being an average on only one month, the mean anomalies are larger. Northern America, Alaska and western Canada are colder than average (minimum around -5°C), while the eastern part, from the United States to Greenland, recorded positive anomalies of 2-3°C. In Eurasia, the areas close to the Arctic Ocean show very positive anomalies, over 10°C, while almost all continent, with the exception of Western Europe, and southeast Asia, show strong negative anomalies, with values between -5°C and -10°C. In the southern hemisphere, the anomalies are less noticeable: slightly negative in Argentina, Chile and Mauritania, and weakly positive in Brazil, South Africa, Australia and Ethiopia; positive, with peaks larger than 5°C over most of Antarctica.

Surface temperature anomaly (° C) on the month of December 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (° C) on the month of December 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Let us now look in more detail the situation on the European continent. Apart from the Arctic (where anomalies exceeded 6°C), we see that the whole Europe, with the exception of Portugal, Great Britain, Scandinavia, Baltic States and a small piece of Russia, was under a positive anomaly, albeit lower than 2°C. The hottest areas include south-eastern Italy, Greece, Romania, Bulgaria, the Black Sea and a strip between Armenia and Azerbaijan.

Surface temperature anomaly (° C) on the period December 2011-February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (° C) on the period December 2011-February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

It is interesting, in this regard, to see also the map of the anomalies of geopotential height at 200 hPa (hereinafter called Z200), a level typical of the lower stratosphere. The graph shows a good correspondence between the positive thermal anomalies of temperature and those positive of Z200, while the negative anomalies of Z200 match with null or slightly negative anomalies of temperature.

200 hPa geopotential height anomaly (in m) relative to the period December 2011-February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

200 hPa geopotential height anomaly (in m) relative to the period December 2011-February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

This finding can also be generalized to a global scale, as the good symmetry between the map of thermal anomaly at ground level and that of the Z200 is still evident. These maps visualize the correlations between tropospheric and stratospheric circulation, not yet fully understood in their details but under study (among others, I cite this 2007 paper in which Cohen et al. discuss the events of interaction between the stratosphere and troposphere in the extratropical regions).

200 hPa geopotential height anomaly (in m) relative to the period December 2011 - February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

200 hPa geopotential height anomaly (in m) relative to the period December 2011 – February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Recently, the National Oceanic and Atmospheric Administration (NOAA) said that, in the continental 48 states of the US, 2012 had an average temperature of 55.3°F (12.9°C), which eclipsed 1998, the previous record holder, by 1°F (0.55°C). The 1°F difference from 1998 is an unusually large margin, considering that annual temperature records are typically broken by just tenths of a degree Fahrenheit. In fact, the entire range between the coldest year on record, which occurred in 1917, and the previous record warm year of 1998 was just 4.2°F.

Let thus see a map centered on the US: the anomaly here tops to more than 3°C between Nebraska and Kansas, and the isotherm 1.5°C contains most of the US.

Surface temperature anomaly (° C) on the period December 2011-February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (° C) on the period December 2011-February 2012 with respect to the 1981-2010 reference period. NOAA-NCEP data.

Now we would see some zooms in some meteorologically interesting periods. The year that has just ended was characterized, overall, by a series of significant weather phenomena. Among others, Italians remember the intense cold wave in first half of February (with extreme thermal values not seen since 1985-86 and, in some areas, heavy snowfalls also in the plains, that created serious problems), the very hot and dry summer in central and southern Italy (probably the warmest of the last 100 years, maybe second only to that of 2003) and the moderate cold wave in early December, which put an end to a long period of above-average temperatures.

Let us start from the first two weeks of February 2012. The thermal maps show Europe completely covered by a negative anomaly (except for part of Scotland and Ireland, and Iceland), with very low values: -12°C. In Italy, the North was the most abnormally cold zone, with values below the average of 7.5-10.5°C, while moving Southwards, the anomaly, even if negative, becomes less conspicuous. Notice also how the mitigating effect of the Mediterranean, who entered in the 2011 winter with temperatures well above average, such as to favors some flooding episodes and even the generation of a Mediterranean hurricane (medicane: see here) near Corsican coasts, was almost absent in the western part.

Surface temperature anomaly (°C) on the period 1 - 14 February 2012, compared to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period 1 – 14 February 2012, compared to the 1981-2010 reference period. NOAA-NCEP data.

Also some Asiatic regions have experienced cold weather at the beginning of the year. The map of the anomalies in the first two months shows a sort of bipolar situation, with a large negative anomaly over most of central and southern Asia, with the exception of the extreme southeast, and another huge and large positive anomaly over Siberia and Arctic sea. It appears as the cold air was displaced southwards of its natural position, and also in this case the map of the Z200 anomaly (not shown) presents some similarities.

Surface temperature anomaly (°C) on the period January  – February 2012, compared to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period January – February 2012, compared to the 1981-2010 reference period. NOAA-NCEP data.

Coming again to Europe, we continue with the warm months: the anomaly map shows a dipolar situation over Europe, with the northwestern part of the continent cold and the rest under the influence of a heat wave that, in Italy, recorded 1.5-2°C above average over the Adriatic regions, and values less than 1°C over the Alps (on this site there are some additional consideration on Italian summer). The most striking positive anomaly was recorded in a narrow strip of land included between Romania and the Black Sea.

Surface temperature anomaly (°C) on the period May-August 2012 compared to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period May-August 2012 compared to the 1981-2010 reference period. NOAA-NCEP data.

Finally, we analyze the situation that characterized the other, most moderate, cold spell of the year, recorded in the first two weeks of December. As in the previous case, the 0°C isotherm contains almost all Europe, except the southern part and the Mediterranean.

Surface temperature anomaly (°C) on the period 1 - 14 December 2012 compared to the 1981-2010 reference period. NOAA-NCEP data.

Surface temperature anomaly (°C) on the period 1 – 14 December 2012 compared to the 1981-2010 reference period. NOAA-NCEP data.

Concerning the rest of the world, everybody remembers the Hurricane Sandy, which flooded entire districts of New York; or the drought in the U.S.; or the extensive flooding caused by tropical cyclones in Madagascar and the Philippines. Fewer people instead remember the Hurricane Nadine, which did not cause serious damages, but stationed off the Azores for over twenty days with the status of a hurricane, going round and round in these parts, and double-tapping islands and giving some concern to meteorologists who feared its explosive entrance in the Mediterranean, fortunately not occurred. Born on Sept. 7, and died on October 4, with its 23 days of life as tropical, subtropical and post-tropical cyclone, of which 21.75 as a tropical/subtropical system, Nadine is ranked as the fifth long-lived hurricane of the history.

Hurricane Nadine photographed on September 15, 2012 (left) and his track from the time of his birth until his death (right).

Hurricane Nadine photographed on September 15, 2012.

Hurricane Nadine photographed on September 15, 2012 (left) and his track from the time of his birth until his death (right).

Hurricane Nadine track from the time of his birth until his death.

Look at the map of the anomalies of sea surface temperature, we can see that, particularly during the period in which Nadine flew over the Atlantic, the anomalies became negative, sign of the potent activity of water mixing carried by the Nadine winds. That is why fishermen, in tropical areas, usually do not fear, but rather wait, and hope, the hurricanes, whose mixing effect cools the surface waters, favoring the fish abundance.

Sea surface temperature anomaly (°C) on the period 15 - 30 September 2012 compared to the 1981-2010 reference period. NOAA-NCEP data.

Sea surface temperature anomaly (°C) on the period 15 – 30 September 2012 compared to the 1981-2010 reference period. NOAA-NCEP data.

Worldwide, the 2012 reserved another resounding record: the marine Arctic ice cap has shrunk as never before in recent decades (see this post by Real Climate): the minimum area occupied by marine ice at the North Pole was only 3.41 million square kilometers, value smaller than one half the average of the last two decades of the twentieth century! Climatologists know well the ice-albedo positive feedback, one of the most important ones. Let us see, therefore, if it is possible to find a direct effect of this anomaly of Arctic marine ice cover on its surface temperatures (SST). Well, the answer is positive: the actual area free of ice is the one that shows the most noticeably positive thermal anomalies, more than 4°C, with a peak of more than 7°C near the islands of Novaya Zemlya. Without detailing here hypotheses that still need further evidence, however, it is impossible to not underline that the ice-free horseshoe structure that, in September, surrounds the Greenland, is also present in the SST thermal anomalies, and has also an impact on the field of sea-level pressure anomaly, whose maxima are shifted on the continents.

Ice extent on September 16, 2012 (from the site NSIDC).

Ice extent on September 16, 2012 (from the site NSIDC).

Sea surface temperature anomaly (°C), related to the period September-December 2012 and compared to the 1981-2010 reference period. NOAA-NCEP data.

Sea surface temperature anomaly (°C), related to the period September-December 2012 and compared to the 1981-2010 reference period. NOAA-NCEP data.

Surface pressure anomaly (hPa) related to the period September-December 2012 and compared to the 1981-2010 reference period. NOAA-NCEP data.

Surface pressure anomaly (hPa) related to the period September-December 2012 and compared to the 1981-2010 reference period. NOAA-NCEP data.

The fear, in this case, is that the scientific findings will be later than the disappearance, in September, of the Arctic sea ice. As it is can be seen below, it may be possible that this fact could happen as early as within 4-5 years …

Estimated sea ice minimum volume from UW PIOMAS, and regression curve.

Estimated sea ice minimum volume from UW PIOMAS, and regression curve.

Last, but not least, we will report another record in 2012. At the remote meteorological station in Barrow, Alaska, for the first time the monthly averaged atmospheric CO2 concentrations exceeded the threshold of 400 ppm (parts per million – that is, over a million molecules of air, more than 400 are CO2) in the months of April and May. We would like to stress that Barrow station is remote, i.e. away from CO2 sources able to influence the measurements. The threshold of 400 ppm is purely psychological, and probably, less than three years later, also the global average will exceed it; however, this figure represents a signal that can not be overlooked, especially considering that other greenhouse gases such as methane, are increasing and every year set a new record of concentration.

The NOAA observatory's atmospheric in Barrow, Alaska.

The NOAA observatory’s atmospheric in Barrow, Alaska.

Note: part of this post has been published in Italian language here.