Thursday, February 21, 2013

New paper finds 'much lower risk' to Amazon from climate change

A paper published today in Nature finds "a much lower risk of Amazon forest dieback under CO2-induced climate change if CO2 fertilization effects are as large as suggested by current models." The paper adds to other recent papers demonstrating the Amazon is resilient to climate change due to CO2 fertilization, and that Amazon trees will tolerate IPCC projected temperature in the year 2100.


Sensitivity of tropical carbon to climate change constrained by carbon dioxide variability


Nature
 
494,
 
341–344
 
(21 February 2013)
 
doi:10.1038/nature11882
Received
 
Accepted
 
Published online
 
The release of carbon from tropical forests may exacerbate future climate change1, but the magnitude of the effect in climate models remains uncertain2. Coupled climate–carbon-cycle models generally agree that carbon storage on land will increase as a result of the simultaneous enhancement of plant photosynthesis and water use efficiency under higher atmospheric CO2concentrations, but will decrease owing to higher soil and plant respiration rates associated with warming temperatures3. At present, the balance between these effects varies markedly among coupled climate–carbon-cycle models, leading to a range of 330 gigatonnes in the projected change in the amount of carbon stored on tropical land by 2100. Explanations for this large uncertainty include differences in the predicted change in rainfall in Amazonia45 and variations in the responses of alternative vegetation models to warming6. Here we identify an emergent linear relationship, across an ensemble of models7, between the sensitivity of tropical land carbon storage to warming and the sensitivity of the annual growth rate of atmospheric CO2 to tropical temperature anomalies8. Combined with contemporary observations of atmospheric CO2 concentration and tropical temperature, this relationship provides a tight constraint on the sensitivity of tropical land carbon to climate change. We estimate that over tropical land from latitude 30° north to 30° south, warming alone will release 53±17 gigatonnes of carbon per kelvin. Compared with the unconstrained ensemble of climate–carbon-cycle projections, this indicates a much lower risk of Amazon forest dieback under CO2-induced climate change if CO2 fertilization effects are as large as suggested by current models9. Our study, however, also implies greater certainty that carbon will be lost from tropical land if warming arises from reductions in aerosols10 or increases in other greenhouse gases11.

Wednesday, February 20, 2013

Europe's cap & trade system is faltering


Europe's Emissions Plan Hits Turbulence

Crisis Hampers Program Aimed at Fighting Global Warming, as Economic Recovery Efforts and Environmental Goals Clash

WSJ.COM 2/20/13: Europe's flagship effort to fight global warming is faltering, despite an effort Tuesday by European parliamentarians to bolster the regional emissions-trading system, as the Continent's governments struggle to balance environmental priorities and pressing economic concerns.
Prices for polluting have plummeted, the result of an oversupply of emissions permits in the European carbon-trading market and slackening demand for electricity amid the Continent's economic woes—a development that is calling into question the effectiveness of similar programs world-wide.
With the cost of emitting carbon dioxide at around €5 ($6.68) a ton, a third of what it was 18 months ago, utilities in the Czech Republic, Germany and Poland have largely lost the incentive to pollute less, and are reconsidering plans to phase out coal-fired plants.
On Tuesday, a committee of the European Parliament moved ahead with a plan aimed at shoring up the market, known as the European Union Emissions Trading System, or ETS, and keeping prices from falling further. The committee delayed the release of 900 million new emissions allowances by up to five years. One permit, or one allowance, equals the right to emit one ton of carbon dioxide.
But despite the committee's action, permit prices slipped further, ending the day Tuesday at €4.58 after closing Monday at €5.12.
Making it more expensive to pollute by requiring companies to buy emissions permits is central to the EU's goal of reducing emissions by 20% in 2020 from 1990 levels. But it would also be an unwelcome drag on a struggling economy.
That has turned decision-making on the permit plan into a tug of war between those more concerned with sparking growth and those arguing that the EU shouldn't lose sight of longer-term environmental goals as part of the international effort to stem global warming.
"There is a disparity between the economic priorities and challenges that Europe is facing and reaching more aggressive emissions reductions," said Divya Reddy, a Washington-based analyst for Eurasia Group who follows climate change.
In Tuesday's vote, EU politicians mustered enough votes for the ETS lifeline plan to move forward, but were unable to agree on much more than that.
The committee delayed a decision on whether to send the plan directly to the Council of Ministers, which would start negotiations among EU member governments, or to first put it before the whole European Parliament, which could drag out the discussions, potentially for months.
Among those arguing most loudly for the primacy of economic concerns is Poland. Polish Environment Minister Marcin Korolec said his government opposes any effort to increase the price of permits. Higher permit prices would make electricity more expensive and threaten his country's economy, which is experiencing a sharp slowdown in growth and rising unemployment, he said. "The ETS was designed as a market mechanism. I believe that it should continue to be operated based on market rules," Mr. Korolec said.
Günther Oettinger, the European energy commissioner, on Monday voiced concerns that EU governments wouldn't be able to agree on the proposed changes.
The longer the process drags on, the further permit prices could slip, some traders said.
EU member states auction off about 60 million allowances a month, according to Milan Hudak, a carbon trader at Virtuse Group Suisse.
Over the past five years, the price of permits has dropped from a high of €28.70 a ton before the global financial crisis started in 2008 to below €3 a ton last month when the European Parliament's industrial committee rejected the plan to delay allowances.
Jan Pravda, director of Pravda Capital Partners, a trader of the allowances, said the problem is that if allowance prices rise, European manufacturers could move operations to countries that lack nationwide emissions-trading systems, such as China or the U.S.
The question is: How deep will the cuts in the number of allowances have to be to get the market functioning effectively again?
"Temporarily taking 900 million tons off the market is too little too late," Mr. Pravda said. "The real oversupply is several billion tons and this 'backloading' isn't taking supply off market but shifting it in time."
Environmental activist groups Climate Action Network and Greenpeace argue that 1.4 billion planned allowances need to be withheld and an additional 2.2 billion outstanding permits should be canceled.
One possibility is for the EU to set minimum prices for permits, an approach taken by California, which held its first auction for emission allowances in November. The average auction price was $10.09 per ton, just above the $10 minimum price. The minimum price will rise 5% each year and be adjusted for inflation. In 2013, for example, the minimum price for a ton of emissions is $10.71.
A minimum price could prevent another crash, Ms. Reddy of Eurasia Group said. "But from a political perspective it looks unlikely," she added.
What happens could well come down to a decision by Germany, which has roughly half the votes needed for a blocking minority that could prevent any changes to the ETS. But German leaders appear split among themselves.
Peter Altmaier, Germany's environment minister, supports the reduction of carbon allowances, while Economics Minister Philipp Rösler is against any plans that would lift power prices.
Mr. Rösler's main argument against the plan is that it would threaten competitiveness and jobs, an Economics Ministry spokeswoman said.

New paper finds Antarctica has been gaining surface ice mass over past 150 years

A paper published today in The Cryosphere finds Antarctica has been gaining surface ice and snow accumulation over the past 150+ years, and finds acceleration in some areas noting, "a clear increase in accumulation of more than 10% has occurred in high Surface Mass Balance coastal regions and over the highest part of the East Antarctic ice divide since the 1960s." Furthermore, the paper notes, "Global climate models suggest that Antarctic snowfall should increase in a warming climate and mitigate rises in the sea level."

Top graph shows the entire Antarctic continent has been gaining surface ice mass over the past 150 years. According to the paper, Antarctic surface ice mass is presently growing by 2100 gigatons per year.
Even the allegedly "vulnerable" West Antarctic Ice Sheet [WAIS] surface mass balance has not changed in 150+ years.

The Cryosphere, 7, 303-319, 2013
www.the-cryosphere.net/7/303/2013/
doi:10.5194/tc-7-303-2013


A synthesis of the Antarctic surface mass balance during the last 800 yr

M. Frezzotti1, C. Scarchilli1, S. Becagli2, M. Proposito1, and S. Urbini3
1ENEA, Agenzia Nazionale per le nuove tecnologie, l'energia e lo sviluppo sostenibile, Rome, Italy
2Department of Chemistry, University of Florence, Sesto F.no, Italy
3INGV, Istituto Nazionale di Geofisica e Vulcanologia,, Rome, Italy

Abstract. Global climate models suggest that Antarctic snowfall should increase in a warming climate and mitigate rises in the sea level. Several processes affect surface mass balance (SMB), introducing large uncertainties in past, present and future ice sheet mass balance. To provide an extended perspective on the past SMB of Antarctica, we used 67 firn/ice core records to reconstruct the temporal variability in the SMB over the past 800 yr and, in greater detail, over the last 200 yr.

Our SMB reconstructions indicate that the SMB changes over most of Antarctica are statistically negligible and that the current SMB is not exceptionally high compared to the last 800 yr. High-accumulation periods have occurred in the past, specifically during the 1370s and 1610s. However, a clear increase in accumulation of more than 10% has occurred in high SMB coastal regions and over the highest part of the East Antarctic ice divide since the 1960s. To explain the differences in behaviour between the coastal/ice divide sites and the rest of Antarctica, we suggest that a higher frequency of blocking anticyclones increases the precipitation at coastal sites, leading to the advection of moist air in the highest areas, whereas blowing snow and/or erosion have significant negative impacts on the SMB at windy sites. Eight hundred years of stacked records of the SMB mimic the total solar irradiance during the 13th and 18th centuries. The link between those two variables is probably indirect and linked to a teleconnection in atmospheric circulation that forces complex feedback between the tropical Pacific and Antarctica via the generation and propagation of a large-scale atmospheric wave train.


 Final Revised Paper (PDF, 8075 KB)   Discussion Paper (TCD)   

Tuesday, February 19, 2013

NYT Op Ed: Hansen & McKibben are 'utterly boneheaded'


How Not to Fix Climate Change


After much back and forth, James E. Hansen and I had agreed on a date to meet. Hansen, the director of NASA’s Goddard Institute for Space Studies, is the scientist most closely associated with climate change activists like Bill McKibben, who has led the charge against the Keystone XL pipeline, and Michael Brune, the executive director of the Sierra Club. In Hansen’s view, the country needs to start moving away from fossil fuels now, before the damage becomes irreversible.
As regular readers knowI believe the Obama administration should approve the Keystone pipeline, which would transport oil mined and processed from the tar sands of Alberta, Canada, to refineries in the Gulf of Mexico. Like it or not, fossil fuels are going to remain the world’s dominant energy source for the foreseeable future, and we are far better off getting our oil from Canada than, say, Venezuela. And the climate change effects of tar sands oil are, all in all, pretty small. I had the strong sense that Hansen hoped that once we met, I would begin to see the error of my ways.
The date we set was on Thursday, Feb. 14. The only glitch, he said, is that on the 13th, he was participating in an anti-Keystone demonstration in front of the White House led by his friend McKibben. The plan was they’d all try to get arrested. “It is conceivable that we will be spending the night of the 13th in the clink, in which case it is not clear when I will arrive on the 14th,” Hansen wrote in an e-mail. (He added, “Yes, I know, the merits of this continuing activity may be dubious, but Bill is working his butt off so hard that I can’t refuse.”) I postponed the meeting.
Suddenly, it appears, the Keystone XL pipeline, which President Obama temporarily blocked during his re-election campaign, is back in the news. The State of Nebraska, which had previously opposed the pipeline, recently dropped its opposition after TransCanada, the company hoping to build it, rerouted portions of it to avoid sensitive lands and aquifers. Canada, still miffed by Obama’s rejection of the pipeline last year, is threatening to sell the oil to China if the United States says no again.
In fact, this should be a no-brainer for the president, for all the reasons I stated earlier, and one more: the strategy of activists like McKibben, Brune and Hansen, who have made the Keystone pipeline their line in the sand, is utterly boneheaded.
Brune and McKibben have been very clear about what they hope to accomplish. Oil companies have invested upward of $100 billion to extract the unconventional oil in the sands. A pipeline is the only way to export it. The Keystone pipeline is Canada’s Plan A. Plan B is a pipeline to British Columbia, which would get the oil to China. If the president blocks Keystone, and the First Nation tribes continue their staunch opposition to the western pipeline, then Canada will have the second largest oil reserves in the world — and no place to sell it. The assumption of the activists is that by choking off the supply of new oil sources like the tar sands, the U.S. — and maybe the world — will be forced to transition more quickly to green energy.
Can you see how backward this logic is? As Adam Brandt, an energy expert at Stanford University, pointed out to me recently, so long as the demand is there, energy producers are going to search for new supplies of fossil fuel — many of them using unconventional means like tar sands extraction. “With growing global demand, the economic pressure to develop unconventional resources is enormous and not going away,” he said. “Can environmental groups expect to win a series of fights for decades to come, when the economic forces are aligned very strongly against them in each round?” The answer is obvious: no. The emphasis should be on demand, not supply. If the U.S. stopped consuming so much of the world’s oil, the economic need for the tar sands would evaporate.
On Monday, I finally spoke to Hansen. His knowledge and sincerity are easy to admire, even if his tactics are not. He told me he would like to see oil companies pay a fee, which would rise annually, based on carbon emissions. He said that such a tax could reduce emissions by 30 percent within 10 years. Well, maybe. But it would also likely make the expensive tar sands oil more viable. If you really want to eliminate expensive new fossil fuel sources, the best way is to lower the price of oil, which would render them uneconomical. But, of course, that wouldn’t exactly lower demand either.
In any case, McKibben, Hansen and others were arrested on Wednesday, as planned. They spent a few hours in jail and paid $100 fines. And that was it.
Until the next time, of course.

NPR claims TV weather forecasters doubt man-made global warming because they 'don't know much about climate'

A highly biased report on NPR today claims that most TV weathercasters are afraid to discuss climate change because they "don't know much about climate science, and many who do are fearful of talking about something so polarizing." However, the poll upon which the NPR report is based instead shows the vast majority of weathercasters have studied the facts regarding climate change and only 19% agree with the IPCC claim that global warming is happening and is caused mostly by human activity. The report also notes, "But even many meteorologists who don't think it's all a hoax still profoundly distrust climate models" because ""They get reminded each and every day anytime their models don't prove to be correct." Note climate models are the same computer models used by weather forecasters, only run for much longer periods of time. Although these models struggle with forecasting tomorrow's weather, climate scientists assure us that they can determine global temperatures a century from now.

Forecasting Climate With A Chance Of Backlash


by JENNIFER LUDDEN NPR

When it comes to climate change, Americans place great trust in their local TV weathercaster, which has led climate experts to see huge potential for public education.

The only problem? Polls show most weather presenters don't know much about climate science, and many who do are fearful of talking about something so polarizing.

In fact, if you have heard a weathercaster speak on climate change, it's likely been to deny it. John Coleman in San Diego and Anthony Watts of Watts Up With That? are among a group of vocal die-hards, cranking out blog posts and videos countering climate science. But even many meteorologists who don't think it's all a hoax still profoundly distrust climate models.

"They get reminded each and every day anytime their models don't prove to be correct," says Ed Maibach, who directs the Center for Climate Change Communication at George Mason University, and has carried out several surveys of TV weathercasters. "For them, the whole notion of projecting what the climate will be 30, 50, a hundred years from now, they've got a fairly high degree of skepticism."

Read the rest at NPR

From the poll of weather forecasters mentioned above

1. Global warming refers to the idea that the world’s average temperature has been increasing over the
past 150 years, may be increasing more in the future, and that the world’s climate may change as a result.

1a. What do you think? Do you think that global warming is happening?

Yes, and it is caused mostly by human activity 19% [as claimed by the IPCC]
Yes, it is caused more-or-less equally by human activity and natural events 35%
Yes, and it is caused mostly by natural events 29%
Don’t know* 8%
No 9%

n=433. * Three respondents skipped this question and were treated as having answered "Don't know."

1b. [If Q1 is Don't know] Which of the following statements best describes why you are undecided about
whether or not global warming is happening?

I haven’t had adequate opportunity to study the facts. 3%
I’m just not interested in the topic. 0%
I have concluded there is equal evidence on both sides of the argument 6%
I have concluded that currently there is insufficient evidence to prove either position. 44%
I have concluded that currently there is insufficient evidence to attribute the relative
contributions of human vs. natural factors. 38%
Other (see Appendix for detailed responses) 9%

n=32 100%

New paper finds IPCC models fail to simulate the most important natural weather patterns

A new paper published in Global and Planetary Change finds that IPCC climate models are unable to reproduce either the El Nino Southern Oscillation [ENSO] or the Indian summer monsoon, the two most influential  natural weather patterns on Earth, both of which have large effects upon global climate. The authors therefore caution that, given these large uncertainties of natural variation, current models cannot be relied upon to project future global warming from greenhouse gases. According to the authors, "More research in improving the current day simulations, improving model capacity to simulate better by improving the greenhouse gases (GHG) and aerosols in the models are some of the important and immediate steps that are necessary."


Revisiting the Indian summer monsoon-ENSO links in the IPCC AR4 projections: A cautionary outlook


  • Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pune, India

Abstract

The climate change experiments under the fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), namely the twentieth century simulations (20C3M) and Special Report on Emissions Scenarios (SRES) A1B, are revisited to study whether these models can reproduce the ENSO and ENSO Modoki patterns as the gravest two modes from statistical linear analysis as observed. The capability of the models in simulating realistic ENSO/ENSO Modoki teleconnections with the Indian summer monsoon, and also the implications for the future is also explored. Results from the study indicate that only ~ 1/4th of the models from 20C3M capture either ENSO or ENSO Modoki pattern in JJAS. Of this 1/4th, only two models simulate both ENSO and ENSO Modoki as important modes. Again, out of these two, only one model simulates both ENSO and ENSO Modoki as important modes during both summer and winter.
It is also shown that the two models that demonstrate ENSO Modoki as well as ENSO associated variance in both 20C3M and SRESA1B represent the links of the ISMR with ENSO reasonably in 20C3M, but indicate opposite type of impacts in SREA1B. With the limited skills of the models in reproducing the monsoon, the ENSO and ENSO Modoki, it is difficult to reconcile that the teleconnections of a tropical driver can change like that. All this indicates the challenges associated with the limitations of the models in reproducing the variability of the monsoons and ENSO flavors, not to speak of failing in capturing the potential impacts of global warming as they are expected to. More research in improving the current day simulations, improving model capacity to simulate better by improving the Green House Gases (GHG) and aerosols in the models are some of the important and immediate steps that are necessary.

Another day, another non-hockey-stick

A paper published today in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs ocean temperatures from corals in the South Pacific and shows temperatures at the end of the record in the year 2000 were not unusual, unnatural, or unprecedented over the past 350 years, and were as warm or warmer in the 1600's during the Little Ice Age.
Add caption
Improving coral-base paleoclimate reconstructions by replicating 350 years of coral Sr/Ca variations

  • a College of Marine Science, University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701, USA
  • b Department of Geography and Anthropology, Louisiana State University, 227 Howe-Russell Geoscience Complex, Baton Rouge, LA 70803, USA
  • c Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, J.J. Pickle Research Campus, Building 196, 10100 Burnet Road R2200, Austin, TX 78758, USA
  • d Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, USA
  • e High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan

Abstract

Coral-based climate reconstructions are typically based on a single record and this lack of replication leads to questions in regards to chronology accuracy and reliability of the inclusive geochemical variations to record climate viability. Here we present two multi-century coral Sr/Ca records recovered from a Porites luteacolony offshore of Amédée Island, New Caledonia (22°28.8′S, 166°27.9′E). The chronology was developed by cross dating the coral Sr/Ca time series and verifying the chronology with high precision absolute 230Th dating. We identify chronological discrepancies of − 2.3 and + 3.7 years century− 1 for reconstructions based on a single core with uncertainty increasing after ~ 250 years. We assess the impact of Porites skeletal architecture on coral geochemistry by characterizing centimeter-scale architectural structures with respect to sampling. Optimal sampling paths are those on the slab surface parallel to the growth direction of individual corallites along the central axis of an actively extending corallite fan. Coral Sr/Ca time series extracted from optimal skeletal structures are highly reproducible with a mean absolute difference of 0.021 mmol mol− 1 or 0.39 °C for monthly determinations. Suboptimal skeletal architecture is characterized by corallites extending through the slab surface, and the coral Sr/Ca determinations derived from suboptimal paths tend to produce a warm bias that varies between + 0.04 and + 2.30 °C. Disorganized skeletal architecture is characterized by small, terminating, or unclear corallite fans that produce a cold bias of − 0.11 to − 2.45 °C in coral Sr/Ca determinations. These problematic architecture types also produce biases in coral δ18O determinations, but to a lesser extent. We assess the impact of sampling a coral colony along paths that vary from vertical to horizontal in large and small Porites colonies with extension rates > 6 mm year− 1and we determine there is no significant difference in the coral Sr/Ca records.

New paper finds climate models are 'inconsistent with past warming'

A new paper published in Environmental Research Letters finds that climate models exaggerate the upper end of projected global warming because the models are "inconsistent with past warming." The paper adds to many other recent peer-reviewed studies demonstrating that IPCC projections of global warming are exaggerated. 


The upper end of climate model temperature projections is inconsistent with past warming

OPEN ACCESS
Peter Stott1, Peter Good1, Gareth Jones1, Nathan Gillett2 and Ed Hawkins3
Show affiliations


Letter

Climate models predict a large range of possible future temperatures for a particular scenario of future emissions of greenhouse gases and other anthropogenic forcings of climate. Given that further warming in coming decades could threaten increasing risks of climatic disruption, it is important to determine whether model projections are consistent with temperature changes already observed. This can be achieved by quantifying the extent to which increases in well mixed greenhouse gases and changes in other anthropogenic and natural forcings have already altered temperature patterns around the globe. Here, for the first time, we combine multiple climate models into a single synthesized estimate of future warming rates consistent with past temperature changes. We show that the observed evolution of near-surface temperatures appears to indicate lower ranges (5–95%) for warming (0.35–0.82 K and 0.45–0.93 K by the 2020s (2020–9) relative to 1986–2005 under the RCP4.5 and 8.5 scenarios respectively) than the equivalent ranges projected by the CMIP5 climate models (0.48–1.00 K and 0.51–1.16 K respectively). Our results indicate that for each RCP [Representative CO2 Concentration Pathway] the upper end of the range of CMIP5 climate model projections is inconsistent with past warming.

Monday, February 18, 2013

New paper demonstrates Arctic temperatures are not unusual, unnatural, or unprecedented

A paper published today in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs Arctic temperatures from shells collected from Iceland and demonstrates that temperatures have been warmer than the present over much of the past 500 years. The paper adds to many other peer-reviewed studies demonstrating that current Arctic temperatures are not unusual, unnatural, or unprecedented. 
Shell growth, a proxy for temperature, has been as high or higher than the present [end of record in the year 2000] during much of the past 500 years. 
Data from a similar study demonstrates that Arctic sea surface temperatures [SSTs] were warmer than the present [year 2000 A.D.] during most of the past 500 years.
 Climate signatures on decadal to interdecadal time scales as obtained from mollusk shells (Arctica islandica) from Iceland

  • a Alfred Wegener Institute for Polar and Marine Research, Bussestr. 24, 27570 Bremerhaven, Germany
  • b Institute of Geosciences, Earth System Science Research Center, University of Mainz, Johann-Joachim-Becher-Weg 21, 55128 Mainz, Germany

Abstract

Pronounced decadal climate oscillations are detected in a multi-centennial record based on shell growth rates of the marine bivalve mollusk, Arctica islandica, from Iceland. The corresponding analysis of patterns in sea level pressure and temperature exhibit large-scale teleconnections with North Atlantic climate quantities. We find that the record projects onto blocking situations in the northern North Atlantic. The associated circulation shows a low-pressure signature over Greenland and the Labrador Sea and a high-pressure system over Western Europe associated with northeasterly flow towards Iceland and weakening in the westerly zonal flow over Europe. It can be speculated that such circulation affects food availability controlling shell growth. On multidecadal time scales, the record shows a pronounced variability linked to North Atlantic temperature. In our record, we find enhanced variability of the shell growth rates on multidecadal time scales, and it appears that this oscillation has high amplitudes in the 16th to 18th century also consistent with marine alkenone data. It is conceivable that these climate oscillations, also linked to sea ice export and enhanced blocking, are a more pronounced feature during times when the climate was relatively cold.

Highlights

► We examine the link between climate and shell growth of Arctica islandica. ► The atmospheric circulation shows a blocking pattern for high shell growth. ► Consistent interpretation of Arctica islandica and high-resolution SST ► We find enhanced multidecadal variability in the 16th to 18th century.  Arctica islandicacan be used as a climate archive for the last 500 years.