Four new papers discuss the relatiosnhip between solar activity and climate: one by Judith Lean (2010) in WIREs Climate Change, a GRL paper by Calogovic et al. (2010), Kulmala et al. (2010), and an on-line preprint by Feulner and Rahmstorf (2010). They all look at different aspects of how changes in solar activity may influence our climate.
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Does global warming make tropical cyclones stronger?
By Stefan Rahmstorf, Kerry Emanuel, Mike Mann and Jim Kossin
Friday marks the official start of the Atlantic hurricane season, which will be watched with interest after last year’s season broke a number of records and e.g. devastated Puerto Rico’s power grid, causing serious problems that persist today. One of us (Mike) is part of a team that has issued a seasonal forecast (see Kozar et al 2012) calling for a roughly average season in terms of overall activity (10 +/- 3 named storms), with tropical Atlantic warmth constituting a favorable factor, but predicted El Nino conditions an unfavorable factor. Meanwhile, the first named storm, Alberto, has gone ahead without waiting for the official start of the season.
In the long term, whether we will see fewer or more tropical cyclones in the Atlantic or in other basins as a consequence of anthropogenic climate change is still much-debated. There is a mounting consensus, however, that we will see more intense hurricanes. So let us revisit the question of whether global warming is leading to more intense tropical storms. Let’s take a step back and look at this issue globally, not just for the Atlantic. [Read more…] about Does global warming make tropical cyclones stronger?
Uncertainty, noise and the art of model-data comparison Incertidumbre, ruido y el arte de comparar datos y modelos
Gavin Schmidt and Stefan Rahmstorf
John Tierney and Roger Pielke Jr. have recently discussed attempts to validate (or falsify) IPCC projections of global temperature change over the period 2000-2007. Others have attempted to show that last year’s numbers imply that ‘Global Warming has stopped’ or that it is ‘taking a break’ (Uli Kulke, Die Welt)). However, as most of our readers will realise, these comparisons are flawed since they basically compare long term climate change to short term weather variability.
This becomes immediately clear when looking at the following graph:
[Read more…] about Uncertainty, noise and the art of model-data comparison
A Galactic glitch
Knud Jahnke and Rasmus Benestad
After having watched a new documentary called the ‘Cloud Mystery’ – and especially the bit about the galaxy (approximately 2 – 4 minutes into the linked video clip) – we realised that a very interesting point has been missed in earlier discussions about ‘climate, galactic cosmic rays and the evolution of the Milky Way galaxy.
It is claimed in ‘The Cloud Mystery’, the book ‘The Chilling Stars’, and related articles that our solar system takes about 250 million years to circle the Milky Way galaxy and that our solar system crosses one of the spiral arms about every ~150 million years (Shaviv 2003).
But is this true? Most likely not. As we will discuss below, this claim is seriously at odds with astrophysical data.
[Read more…] about A Galactic glitch
Data presentation: A trend lesson
I just came across an interesting way to eliminate the impression of a global warming. A trick used to argue that the global warming had stopped, and the simple recipe is as follows:
Does a slow AMOC increase the rate of global warming?
Established understanding of the AMOC (sometimes popularly called Gulf Stream System) says that a weaker AMOC leads to a slightly cooler global mean surface temperature due to changes in ocean heat storage. But now, a new paper in Nature claims the opposite and even predicts a phase of rapid global warming. What’s the story?
By Stefan Rahmstorf and Michael Mann
In 1751, the captain of an English slave-trading ship made a historic discovery. While sailing at latitude 25°N in the subtropical North Atlantic Ocean, Captain Henry Ellis lowered a “bucket sea-gauge” down through the warm surface waters into the deep. By means of a long rope and a system of valves, water from various depths could be brought up to the deck, where its temperature was read from a built-in thermometer. To his surprise Captain Ellis found that the deep water was icy cold.
These were the first ever recorded temperature measurements of the deep ocean. And they revealed what is now known to be a fundamental feature of all the world oceans: deep water is always cold. The warm waters of the tropics and subtropics are confined to a thin layer at the surface; the heat of the sun does not slowly warm up the depths as might be expected. Ellis wrote:
“This experiment, which seem’d at first but mere food for curiosity, became in the interim very useful to us. By its means we supplied our cold bath, and cooled our wines or water at pleasure; which is vastly agreeable to us in this burning climate.”
[Read more…] about Does a slow AMOC increase the rate of global warming?
Ten years of RealClimate: Thanks
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.
El Niño and the record years 1998 and 2016
2017 is set to be one of warmest years on record. Gavin has been making regular forecasts of where 2017 will end up, and it is now set to be #2 or #3 in the list of hottest years:
With update thru September, ~80% chance of 2017 being 2nd warmest yr in the GISTEMP analysis (~20% for 3rd warmest). pic.twitter.com/k3CEM9rGHY
— Gavin Schmidt (@ClimateOfGavin) October 17, 2017
In either case it will be the warmest year on record that was not boosted by El Niño. I’ve been asked several times whether that is surprising. After all, the El Niño event, which pushed up the 2016 temperature, is well behind us. El Niño conditions prevailed in the tropical Pacific from October 2014 throughout 2015 and in the first half of 2016, giving way to a cold La Niña event in the latter half of 2016. (Note that global temperature lags El Niño variations by several months so this La Niña should have cooled 2017.) [Read more…] about El Niño and the record years 1998 and 2016
Scientists respond to Barton
by Gavin Schmidt and Stefan Rahmstorf
Many readers will be aware that three scientists (two of which are contributors to this site, Michael Mann and Ray Bradley) have received letters from Representative Joe Barton (Texas), Chairman of the House Energy and Commerce Committee specifically requesting information about their work on the ‘hockey stick’ papers (Mann et al (1998) and Mann et al (1999)) as well as an enormous amount of irrelevant material not connected to these studies.
Many in the scientific community would welcome any genuine interest in climate change from the committee, but the tone and content of these letters have alarmed many scientists and their professional organisations. In the words of Alan Leshner, CEO of the American Association for the Advancement of Science, the Barton letters “give the impression of a search for some basis on which to discredit these particular scientists and findings, rather than a search for understanding.” Other organisations and individual scientists have also expressed strong concerns: [Read more…] about Scientists respond to Barton
The new IPCC climate report
The time has come: the new IPCC report is here! After several years of work by over 800 scientists from around the world, and after days of extensive discussion at the IPCC plenary meeting in Stockholm, the Summary for Policymakers was formally adopted at 5 o’clock this morning. Congratulations to all the colleagues who were there and worked night shifts. The full text of the report will be available online beginning of next week. Realclimate summarizes the key findings and shows the most interesting graphs.
Update 29 Sept: Full (un-copyedited) report available here.
Global warming
It is now considered even more certain (> 95%) that human influence has been the dominant cause of the observed warming since the mid-20th century. Natural internal variability and natural external forcings (eg the sun) have contributed virtually nothing to the warming since 1950 – the share of these factors was narrowed down by IPCC to ± 0.1 degrees. The measured temperature evolution is shown in the following graph.
Figure 1 The measured global temperature curve from several data sets. Top: annual values. Bottom: averaged values over a decade.
[Read more…] about The new IPCC climate report