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And so it goes – another year, another annual data point. As has become a habit (2009, 2010), here is a brief overview and update of some of the most relevant model/data comparisons. We include the standard comparisons of surface temperatures, sea ice and ocean heat content to the AR4 and 1988 Hansen et al simulations.

First, a graph showing the annual mean anomalies from the IPCC AR4 models plotted against the surface temperature records from the HadCRUT3v, NCDC and GISTEMP products (it really doesn’t matter which). Everything has been baselined to 1980-1999 (as in the 2007 IPCC report) and the envelope in grey encloses 95% of the model runs.

The La Niña event that emerged in 2011 definitely cooled the year a global sense relative to 2010, although there were extensive regional warm extremes. Differences between the observational records are mostly related to interpolations in the Arctic (but we will check back once the new HadCRUT4 data are released). Checking up on our predictions from last year, I forecast that 2011 would be cooler than 2010 (because of the emerging La Niña), but would still rank in the top 10. This was true looking at GISTEMP (2011 was #9), but not quite in HadCRUT3v (#12) or NCDC (#11). However, this was the warmest year that started off (DJF) with a La Niña (previous La Niña years by this index were 2008, 2001, 2000 and 1999 using a 5 month minimum for a specific event) in the GISTEMP record, and the second warmest (after 2001) in the HadCRUT3v and NCDC indices. Given current indications of only mild La Niña conditions, 2012 will likely be a warmer year than 2011, so again another top 10 year, but not a record breaker – that will have to wait until the next El Niño.

People sometimes claim that “no models” can match the short term trends seen in the data. This is not true. For instance, the range of trends in the models for 1998-2011 are [-0.07,0.49] ºC/dec, with MRI-CGCM (run5) the laggard in the pack, running colder than observations.

In interpreting this information, please note the following (repeated from previous years):

• Short term (15 years or less) trends in global temperature are not usefully predictable as a function of current forcings. This means you can’t use such short periods to ‘prove’ that global warming has or hasn’t stopped, or that we are really cooling despite this being the warmest decade in centuries.
• The AR4 model simulations were an ‘ensemble of opportunity’ and vary substantially among themselves with the forcings imposed, the magnitude of the internal variability and of course, the sensitivity. Thus while they do span a large range of possible situations, the average of these simulations is not ‘truth’.
• The model simulations use observed forcings up until 2000 (or 2003 in a couple of cases) and use a business-as-usual scenario subsequently (A1B). The models are not tuned to temperature trends pre-2000.
• Differences between the temperature anomaly products is related to: different selections of input data, different methods for assessing urban heating effects, and (most important) different methodologies for estimating temperatures in data-poor regions like the Arctic. GISTEMP assumes that the Arctic is warming as fast as the stations around the Arctic, while HadCRUT3v and NCDC assume the Arctic is warming as fast as the global mean. The former assumption is more in line with the sea ice results and independent measures from buoys and the reanalysis products.
• Model-data comparisons are best when the metric being compared is calculated the same way in both the models and data. In the comparisons here, that isn’t quite true (mainly related to spatial coverage), and so this adds a little extra structural uncertainty to any conclusions one might draw.

Foster and Rahmstorf (2011) showed nicely that if you account for some of the obvious factors affecting the global mean temperature (such as El Niños/La Niñas, volcanoes etc.) there is a strong and continuing trend upwards. An update to that analysis using the latest data is available here – and shows the same continuing trend:

There will soon be a few variations on these results. Notably, we are still awaiting the update of the HadCRUT (HadCRUT4) product to incorporate the new HadSST3 dataset and the upcoming CRUTEM4 data which incorporates more high latitude data (Jones et al, 2012). These two changes will impact the 1940s-1950s temperatures, the earliest parts of the record, the last decade, and will likely affect the annual rankings (and yes, I know that this is not particularly significant, but people seem to care).

Ocean Heat Content

Figure 2 is the comparison of the ocean heat content (OHC) changes in the models compared to the latest data from NODC. As before, I don’t have the post-2003 AR4 model output, so I have extrapolated the ensemble mean to 2012 (understanding that this is not ideal). New this year, are the OHC changes down to 2000m, as well as the usual top-700m record, which NODC has started to produce. For better comparisons, I have plotted the ocean model results from 0-750m and for the whole ocean. All curves are baselined to the period 1975-1989.

I’ve left off the data from the Lyman et al (2010) paper for clarity, but note that there is some structural uncertainty in the OHC observations. Similarly, different models have different changes, and the other GISS model from AR4 (GISS-EH) had slightly less heat uptake than the model shown here.

As can be seen the long term trends in the models match those in the data, but the short-term fluctuations are both noisy and imprecise. As an aside, there are a number of comparisons floating around using only the post 2003 data to compare to the models. These are often baselined in such a way as to exaggerate the model data discrepancy (basically by picking a near-maximum and then drawing the linear trend in the models from that peak). This falls into the common trap of assuming that short term trends are predictive of long-term trends – they just aren’t (There is a nice explanation of the error here).

Summer sea ice changes

Sea ice changes this year were dramatic, with the Arctic September minimum reaching record (or near record) values (depending on the data product). Updating the Stroeve et al, 2007 analysis (courtesy of Marika Holland) using the NSIDC data we can see that the Arctic continues to melt faster than any of the AR4/CMIP3 models predicted.

This may not be true for the CMIP5 simulations – but we’ll have a specific post on that another time.

Hansen et al, 1988

Finally, we update the Hansen et al (1988) comparisons. Note that the old GISS model had a climate sensitivity that was a little higher (4.2ºC for a doubling of CO2) than the best estimate (~3ºC) and as stated in previous years, the actual forcings that occurred are not exactly the same as the different scenarios used. We noted in 2007, that Scenario B was running a little high compared with the forcings growth (by about 10%) using estimated forcings up to 2003 (Scenario A was significantly higher, and Scenario C was lower).

The trends for the period 1984 to 2011 (the 1984 date chosen because that is when these projections started), scenario B has a trend of 0.28+/-0.05ºC/dec (95% uncertainties, no correction for auto-correlation). For the GISTEMP and HadCRUT3, the trends are 0.18+/-0.05 and 0.17+/-0.04ºC/dec. For reference, the trends in the AR4 models for the same period have a range 0.21+/-0.16 ºC/dec (95%).

As we stated before, the Hansen et al ‘B’ projection is running warm compared to the real world (exactly how much warmer is unclear). As discussed in Hargreaves (2010), while this simulation was not perfect, it has shown skill in that it has out-performed any reasonable naive hypothesis that people put forward in 1988 (the most obvious being a forecast of no-change). However, the use of this comparison to refine estimates of climate sensitivity should be done cautiously, as the result is strongly dependent on the magnitude of the assumed forcing, which is itself uncertain. Recently there have been some updates to those forcings, and so my previous attempts need to be re-examined in the light of that data and the uncertainties (particular in the aerosol component). However, this is a complicated issue, and requires more space than I really have here to discuss, so look for this in an upcoming post.

Overall, given the latest set of data points, we can conclude (once again) that global warming continues.

References

1. G. Foster, and S. Rahmstorf, "Global temperature evolution 1979–2010", Environmental Research Letters, vol. 6, 2011, pp. 044022-. DOI.
2. P.D. Jones, D.H. Lister, T.J. Osborn, C. Harpham, M. Salmon, and C.P. Morice, "Hemispheric and large-scale land surface air temperature variations: An extensive revision and an update to 2010", Journal of Geophysical Research. DOI.
3. J.C. Hargreaves, "Skill and uncertainty in climate models", Wiley Interdisciplinary Reviews: Climate Change, vol. 1, 2010, pp. 556-564. DOI.

För många år sedan kom det fram forskningsresultat som visade att vanliga människor var intresserade av att innerstäderna skulle bli mer bilfria. Forskningen visade också att de flesta politiker tyckte likadant. Det mest intressanta var dock att politikerna inte trodde att vanligt folk ville ha det så, och därför blev det heller inte så.

Gång på gång får vi bevis för att våra politiker går i otakt med sina väljare i en mängd frågor. Idag vet vi från opinionsundersökningar att de flesta är positiva till den nya utsläppsavgiften på flygresor för klimatets skull, men det tog väldigt lång tid att få till dem.

Om du frågar våra politiker så tycker de flesta att styrningen skall vara evidensbaserad, dvs grunda sig på forskning och beprövad vetenskap. Men när det kommer till kritan så agerar man inte så. Just nu har vi läst i bladen hur en politiker i Malmö tycker vi skall strunta i att bygga höghastighetståg och istället satsa på flyget, och då kan vi ju åka kollektivt till flygplatsen.

När jag för ett år sedan höll ihop ett seminarium med ca 80 beslutsfattare, de flesta politiker, som skulle fatta beslut om en ny strategi för kollektivtrafiken i ett av sydliga våra län, gjorde jag som jag ofta gör och lät dem svara på mentometorfrågor kring en mängd frågor, bl a hur man tog sig till mötet. Då visade det sig att av de 80 närvarande hade två cyklat, två åkt  kollektivt och resten åkt bil. Jag frågade dem då hur de tänkte, när de själv inte trodde på sin egen produkt. Som om Volvochefen skulle åkt Mercedes.


Att inte leva som man lär, att fiffla och prata i egen sak verkar vara lika vanligt både till höger och vänster. Makt korrumperar brukar man säga, och även om det inte går så lång,t så tycks tanken att man som politiker skulle lyssna på folket och leva som man lär, bli allt mer sällsynt.

Idag på den välbesökta konferensen om mobility management i Malmö, som vi ordnat tillsammans med danska och svenska aktörer, berättade trafikverket om det stora gap som finns mellan de mål som våra politiker satt upp för minskningen av utsläppen från trafiken, och hur långt man når med de åtgärder man fattat beslut om.  Och det visade sig att det finns inga planer på hur man skall lyckas sluta detta gap.

När skall vi få politiker som lever som de lär, fattar beslut grundat på beprövad vetenskap, lyssnar på folket och leder utvecklingen mot ett hållbart samhälle?

Länk:

MM Öresund 

Just nu ringer det många annonsförsäljare till SLU. När de fått nej från kommunikationsavdelningen ringer de vidare till institutioner och centrumbildningar.  Det finns naturligtvis inget hinder för...

(Bygga/bo)

(Övrigt)

(Avfall/återvinning)

(Trafik/transporter)

(Kemikalier)

(Kemikalier)

(Energi)

(Lag och rätt, Klimat)

Miljö och hållbar utveckling ska integreras i utbildningen.

Kritiserad och delvis oprövad teknik får ny luft under vingarna.

Kritiserad och delvis oprövad teknik får ny luft under vingarna.

Naturvårdsverket menar att pengarna inte räcker för att köpa loss skogarna som behöver skyddas långsiktigt.

Trots att Coop förbjudit ålförsäljning i sina butiker har man kunnat få sätta sina tänder i den akut hotade fisken i Skåne.

Antarktis mystiska undervattensjöar triggar forskare från flera stormakter. Nu har en rysk expedition borrat sig genom den tre kilometer tjocka isen.

Nu har man tagit ett beslut, trots oenighet.

Nu ger det statliga energibolaget sin version av vad som egentligen hände förra året när kärnkraftsreaktorn i Ringhals tvingades stänga ner på grund av en brand i en dammsugare.

Naturskyddsföreningen varnar för tandlös EU-lagstiftning mot farliga kemikalier i vattenmiljöer.