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The mystery of the offset chronologies: Tree rings and the volcanic record of the 1st millennium

19 Feb 2015 by group

Guest commentary by Jonny McAneney

Volcanism can have an important impact on climate. When a large volcano erupts it can inject vast amounts of dust and sulphur compounds into the stratosphere, where they alter the radiation balance. While the suspended dust can temporarily block sunlight, the dominant effect in volcanic forcing is the sulphur, which combines with water to form sulphuric acid droplets. These stratospheric aerosols dramatically change the reflectivity, and absorption profile of the upper atmosphere, causing the stratosphere to heat, and the surface to cool; resulting in climatic changes on hemispheric and global scales.

Interrogating tree rings and ice cores

Annually-resolved ice core and tree-ring chronologies provide opportunities for understanding past volcanic forcing and the consequent climatic effects and impacts on human populations. It is common knowledge that you can tell the age of a tree by counting its rings, but it is also interesting to note that the size and physiology of each ring provides information on growing conditions when the ring formed. By constructing long tree ring chronologies, using suitable species of trees, it is possible to reconstruct a precisely-dated annual record of climatic conditions.

Ice cores can provide a similar annual record of the chemical and isotopic composition of the atmosphere, in particular volcanic markers such as layers of volcanic acid and tephra. However, ice cores can suffer from ambiguous layers that introduce errors into the dating of these layers of volcanic acid. To short-circuit this, attempts have been made to identify know historical eruptions within the ice records, such as Öraefajökull (1362) and Vesuvius (AD 79). This can become difficult since the ice chronologies can only be checked by finding and definitively identifying tephra (volcanic glass shards) that can be attributed to these key eruptions; sulphate peaks in the ice are not volcano specific.

Thus, it is fundamentally important to have chronological agreement between historical, tree-ring and ice core chronologies: The ice cores record the magnitude and frequency of volcanic eruptions, with the trees recording the climatic response, and historical records evidencing human responses to these events.

But they don’t quite line up…
[Read more…] about The mystery of the offset chronologies: Tree rings and the volcanic record of the 1st millennium

Filed Under: Aerosols, Climate Science, Paleoclimate

Unforced Variations: Feb 2015

7 Feb 2015 by group

This month’s open thread.

Filed Under: Climate Science, Open thread

Unforced Variations: Jan 2015

7 Jan 2015 by group

This month’s open thread. Sorry for the slow start – you know what it’s like after the holidays…

Filed Under: Climate Science, Open thread

AGU 2014

14 Dec 2014 by group

Once more unto the breach!

Fall AGU this year will be (as last year)

…the largest Earth Science conference on the planet, and is where you will get previews of new science results, get a sense of what other experts think about current topics, and indulge in the more social side of being a scientist.

[Read more…] about AGU 2014

Filed Under: Climate Science, Communicating Climate, Scientific practice

Ten Years of RealClimate: Where now?

14 Dec 2014 by group

rc10The landscape for science blogging, the public discourse on climate and our own roles in the scientific community have all changed radically over the last 10 years. Blogging is no longer something that stands apart from professional communications, the mainstream media or new online start-ups. The diversity of voices online has also increased widely: scientists blogging and interacting directly with the public via Twitter and Facebook are much more prevalent than in 2004. The conversations have also changed, and (for the most part) have become more nuanced. And a bunch of early career researchers with enthusiasm, time to spare and things to say, have morphed into institute directors and administrators with lots of new pressures. Obviously, blogging frequency has decreased in the last year or so in response to these pressures and this raises the question: where does RealClimate go now?

[Read more…] about Ten Years of RealClimate: Where now?

Filed Under: Climate Science, Communicating Climate, Reporting on climate

Ten Years of RealClimate

10 Dec 2014 by group

rc10In the spring of 2004, when we (individually) first started talking to people about starting a blog on climate science, almost everyone thought it was a great idea, but very few thought it was something they should get involved in. Today, scientists communicating on social media is far more commonplace. On the occasion of our 10 year anniversary today it is worth reflecting on the impact of those changes, what we’ve learned and where we go next.

[Read more…] about Ten Years of RealClimate

Filed Under: Climate Science, Communicating Climate

Ten years of RealClimate: Thanks

10 Dec 2014 by group

rc10 As well as the current core team – David Archer, Eric Steig, Gavin Schmidt, Mike Mann, Rasmus Benestad, Ray Bradley, Ray Pierrehumbert, Stefan Rahmstorf – this blog has had input from many others over the years:

The 90+ guest contributors and previous team members who bring a necessary diversity of experience and expertise to the blog: Abby Swann, Alan Robock, Anders Levermann, Andrew Monaghan, Andy Baker, Andy Dessler, Axel Schweiger, Barry Bickmore, Bart Strengers, Bart Verheggen, Beate Liepert, Ben Santer, Brian Helmuth, Brian Soden, Brigitte Knopf, Caspar Ammann, Cecilia Bitz, Chris Colose, Christopher Hennon, Corrine LeQuere, Darrell Kaufman, David Briske, David Karoly, David Ritson, David Vaughan, Dim Coumou, Dirk Notz, Dorothy Koch, Drew Shindell, Ed Hawkins, Eugenie Scott, Figen Mekik, Francisco Doblas-Reyes, Frank Zeman, Geert Jan van Oldenborgh, Georg Feulner, Georg Hoffmann, George Tselioudis, Jacob Harold, Jared Rennie, Jason West, Jeffrey Pierce, Jim Bouldin, Jim Prall, John Fasullo, Joy Shumake-Guillemot, Juliane Fry, Karen Shell, Keith Briffa, Kelly Levin, Kevin Brown, Kevin Trenberth, Kim Cobb, Kyle Swanson, Loretta Mickley, Marco Tedesco, Mark Boslough, Martin Manning, Martin Vermeer, Matt King, Matthew England, Mauri Pelto, Michael Bentley, Michael Oppenheimer, Michael Tobis, Michelle L’Heureux, Natassa Romanou, Paul Higgins, Peter Minnett, Phil Jones, Pippa Whitehouse, PubPeer, Raimund Muscheler, Rein Haarsma, Richard Millar, Robert Rohde, Ron Lindsay, Ron Miller, Russell Seitz, Sarah Feakins, Scott Mandia, Scott Saleska, Simon Lewis, Spencer Weart, Stephen Schneider, Steve Ghan, Steve Sherwood, Sybren Drijfhout, Tad Pfeffer, Tamino, Terry Gerlach, Thibault de Garidel, Thomas Crowley, Tim Osborn, Tom Melvin, Urs Neu, Vicky Slonosky, William Anderegg, William Connolley and Zeke Hausfather;

The thousands of commenters that have enlivened the conversation and explored many issues in more depth than is possible in the main posts;

The translators of hundreds of posts into Polish, French, Czech, German, Italian, Spanish, Turkish, Mandarin etc;

Miloslav Nic for his “Guide to RC” which provides a comprehensive set of indexes to the content here;

Ryan and the internet service providers at Peer, and now Webfaction, that have helped deal with the many technical challenges and to Environmental Media Services and later, the Science Communication Network, for covering some of those costs;

A sincere thanks to all.

Filed Under: Climate Science

Ten years of Realclimate: By the numbers

10 Dec 2014 by group

rc10Start date: 10 December 2004

Number of posts: 914

Number of comments: ~172,000

Number of comments with inline responses: 14,277

Minimum number of total unique page visits, and unique views, respectively: 19 Million, 35 Million

Number of guest posts: 100+

Number of mentions in newspaper sources indexed by LexisNexis: 225

Minimum number of contributors and guest authors: 105

Minimum number of times RealClimate was hacked: 2

Busiest month: December 2009

Busiest day of the week: Monday

Number of times the IPCC and the NIPCC are mentioned, respectively: 357, 5

Minimum number of Science papers arising from a blog post here: 1

Minimum number of RealClimate mentions in Web Of Science references: 14

Minimum number of RealClimate mentions in theses indexed by ProQuest: 33

Posts highest ranked by Google by year:

2004 CO2 in ice cores
2005 Water vapour: feedback or forcing?
2006 Al Gore’s Movie
2007 Swindled!
2008 FAQ on climate models
2009 The CRU Hack
2010 Feedback on cloud feedback
2011 Misdiagnosis of surface temperature feedback
2012 Extremely Hot
2013 The new IPCC climate report
2014 Climate response estimates from Lewis and Curry

All numbers are estimates from latest available data, but no warranty is implied or provided so all use of these numbers is at your own risk.

Filed Under: Climate Science, Communicating Climate

Unforced variations: Dec 2014

3 Dec 2014 by group

This month’s open thread. Think history, Lima, and upcoming additions of a single data point to timeseries based on arbitrary calendrical boundaries.

Filed Under: Climate Science, Open thread

Unforced variations: Nov 2014

2 Nov 2014 by group

This month’s open thread. In honour of today’s New York Marathon, we are expecting the fastest of you to read and digest the final IPCC Synthesis report in sub-3 hours. For those who didn’t keep up with the IPCC training regime, the Summary for Policy Makers provides a more accessible target.

Also in the news, follow #ArcticCircle2014 for some great info on the Arctic Circle meeting in Iceland.

Filed Under: Climate Science, IPCC, Open thread

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