The Offshore Voyaging Reference Site

Our Changing Oceans

There can be very few offshore cruising boats that don’t have at least one book by Jimmy Cornell aboard—World Cruising Routes, World Voyage Planner or World Cruising Destinations, for example. Drawing on his experiences from nearly forty years of cruising he has successfully developed a range of authoritative books that are indispensable to the ocean traveler.

Cornell Ocean Atlas

Having bought several of his books over the years, I thought that he’d pretty much covered all the angles, until I saw his latest publication, the Cornell Ocean Atlas, and realized that this might well be the best thing he has ever done. And then the next that I heard was that he and the team at Cornell Sailing were planning a new rally that aimed to raise awareness of climate change, with a particular focus on the Northwest Passage.

Fascinating stuff, so I made contact with Jimmy, who kindly agreed to give Attainable Adventure Cruising readers some background on these most recent developments.

Better Data

Looking to develop a new ocean pilot guide, Jimmy found that he was limited to using the original pilot charts developed in the mid-1800s by Lt. Maury of the US Navy. Jimmy mentioned this to his son, Ivan, a computer scientist, who assured him that if he could get access to the latest geospatial and remote buoy sensing ocean and current data, he could develop an algorithm to interrogate and interpret those data in a way that would bring the pilot chart concept completely up to date. Finding that the last 20 years of National Oceanic and Atmospheric Administration (NOAA) and Earth and Space Research (ESR) data measurements of winds and ocean currents were in the public domain, Ivan set to work. And the results are highly impressive.

These new charts have enabled comparisons to be made with the original pilot charts, and show that along many of the world’s most popular cruising routes there have been significant changes in recent years, particularly in terms of seasons, wind speed and direction. Jimmy is confident that the wind data is spot on, with a high degree of accuracy, but points out that with ocean currents the picture is more complicated due to the nature of such currents and their local and regional variability, as is well understood by ocean navigators.

A World of Change

Whether or not you are a believer in anthropogenic climate change, Jimmy points out that these changes are undeniably real. He tells me that this is making it necessary to regularly update his other works—he’s currently hard at work on the seventh edition of World Cruising Routes as a result.

Jimmy believes that in the future this information will be of most use to the ocean sailor in a digital format, available via an app that he and Ivan hope to launch very soon, which will enable a far greater degree of interaction, and will also have the benefit of being much easier to update—cutting edge stuff that will benefit all serious cruising sailors.

I’m interested in learning how he views his recent exposure to the stark, harsh numbers of climate change and its effects on the oceans. Delving into the world of climate science is a bit like opening Pandora’s Box on an intellectual level, and the implications of future effects can’t fail to affect anyone with children or, in his case, grandchildren too. The future ain’t what it used to be. How has it influenced his thinking?

Not In Denial

Jimmy says that he is constantly dismayed by the level of denial of climate change he encounters in his travels. He points out that

sailors are far more aware of what’s happening out on the oceans, and don’t question that change is taking place, [they] just simply deal with it. And anyone who doesn’t believe it’s happening should just go out and sail the Northwest Passage!

Blue Planet Odyssey

Which is exactly what he proposes to do in his latest venture, the Blue Planet Odyssey, to highlight climate change.

Jimmy, of course, has plenty of form when it comes to such events, not least as the creator of the original game-changing Atlantic Rally for Cruisers. But he also subsequently took the whole concept in a totally new direction with the Millenium Odyssey where the participants carried a symbolic flame as a message of peace and goodwill to troubled areas around the world, culminating with an audience with Pope John Paul II. And this new rally has equally ambitious, yet different, aims.

We will be working with some of the islands most affected by climate change—Tuvalu and Tokelau, for example—helping them in practical ways, through our association with organisations like Oceanswatch, and using some of the skills of the Odyssey participants. And we’ll be working with several scientific organisations that are focusing on climate change, including NOAA through having the participating yachts deploy drifter buoys that measure ocean currents, sea surface temperatures and other environmental parameters in some of the remoter areas.

So far the response from cruisers has been enthusiastic and, only eight months since its inception, 24 yachts have signed up to take part, so it would seem that a chord has been struck.

Raising Awareness

Raising awareness of the scale of the problem and its impact on island communities is a primary goal of the rally, and a major media program is being developed to highlight their plight. And the crews of all participating yachts are being encouraged to forge links between their local schools and community and the schools on the islands to promote wider understanding of what it means to have your whole way of life affected by climate change. “The kids in those islands know that their future and their way of life are threatened,” says Jimmy.

And, in a grand gesture, at least some of the boats will attempt to transit the Northwest Passage, now largely possible as a result of climate change—as potent a symbol of the recent changes in our marine environment as can be imagined.

A New Boat For The Cornells

Jimmy is currently having a new aluminium expedition yacht built especially so that he can lead this section of the event. I mention that I see that he is taking his granddaughter Nera with him on this leg, but he counters with, “No, in fact I’m joining her—it was her insistence that I find a boat that would take us, that made me order the new boat.”

It seems that the Cornell spirit is being passed down the generations and that the need to safeguard their future is being passed back up to Jimmy.

A New Challenge For The Cornells

Never one to step back from a challenge, he’s certainly taken on a big one this time, as convincing anyone who’ll listen to recognize climate change and alter course to avoid its worst effects will not be easy. But Jimmy and the family team at Cornell Sailing are determined to try, and in my view they deserve our respect and support for doing so.

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Erik de Jong

This is great!
I’ve been studying and watching the high latitudes since ’89, and sailing them since ’95. And I’m scared by how much faster these changes are developing since 2007/2008. I’ve been searching for info like this, but was never able to find accurate data.
The only problem is that this remains accurate for only a short period of time, especially in the Arctic regions. This work has to be subject to continuous updates from many different sources to become and remain accurate.

Amazing job!

Colin Speedie

Hi Erik

You’re absolutely right – this will remain a work in progress. But that’s what Jimmy and Ivan have in mind, hence their foresight in working towards digital forms of the data which will be much easier to update.

For the most part, the book will be ideal – I have bought a copy and I certainly find it well worth the cost. The speed of the change is likely to be slow enough that the book will outlast me!

But it’s causing Jimmy a lot of work, because all of his publications tend to rely on this data – so many of the books are having to be updated to reflect the changes they have identified – he was busy working on the seventh edition of one of his books when we spoke.

Best wishes


Dick Stevenson

Dear Colin,
Another superb article. I really appreciate your “News of the (sailing) World” writings, both historical and present day. They enrich my sailing life.
Thanks, Dick Stevenson, s/v Alchemy

Colin Speedie

Hi Dick

Thanks very much for that – quite made my day!

I’ll try to keep ’em coming.

Kindest regards


richard s.

when most of us hear about climate change we often equate it with global warming…if that is indeed the culprit then, as reported yesterday by barbara hollingsworth of cnsnews (, we might be able to breathe a little easier…to wit: she reports noaa’s latest studies (state of the climate report for 2012) show that while arctic sea ice coverage is at record lows, antarctic sea ice is at a record high 7.51 million mi sq…she also quotes meteorologist joe bastardi (weather channel ?) to the effect that current temps at the north pole are well below normal…near coldest ever recorded for this time of year and that arctic sea ice coverage loss is slowing…she also reported that recent declines in overall sun spot activity on our closest star (ol’ sol) continues to decline, which, many scientists agree, she says, augurs well for impending global cooling (or, maybe at least slow-down in global warming ?)…obviously an overall highly complicated phenomenom where climate change is concerned but one that is nonetheless important…cheers

richard s., s/v lakota, tampa bay

Colin Speedie

Hi Richard

I suspect there will be many short term ups and downs that will puzzle even the brightest minds. Far smarter people than I tell me to watch the long term trends to see what’s really happening – so that’s what I do.

Not to pour cold water on what might be good news, you understand….

Best wishes


Erik de Jong

This year is indeed slightly better than last year, but still quite far below the average of the last 30 years. And don’t forget that the 30 years average goes a bit lower every year, bringing the “standard to meet” lower and lower. The last 6 years, the lower end of the average ice extent has not been met.

And ice coverage is one thing, ice thickness is a whole different story.
In addition to this, a stretch of water with only 15% of ice coverage, is counted as completely covered. Seasons where the ice is very broken up and spread out count as seasons with a large ice extent, while the absolute amount of ice might even be less.

I would really like to believe that the melting process can be stopped, or at least put to a halt. But I don’t believe this is possible.

Something that might be of interest: the movie “chasing ice” is really something to watch, and is a real eye opener of the consequences of global warming.

I know that I will reduce my carbon footprint as much as I can, I’m currently at less than 10% of the average North-American, I know it will not help turning this problem around, but we have to start somewhere. And maybe a good example will get followers…

richard s.


Marc Dacey

I would be interested to compare and contrast the free US pilot charts with Mr. Cornell’s new work. I would also be intrigued to learn if the newer information about changing wind directions and strengths in certain areas would affect his popular World Cruising Routes, which are predicated, of course, on a high probability of favourable winds for a given route at a given time of the season.

Climate change is just that: change. The change appears to be throttled by factors both cyclical (orbital and sunspot/solar radiation variation) and man-made (pollution). Whether the weather is “worse” or not is highly subjective; what is becoming clearer is that it is less predictable in many areas. That’s a direct challenge to the validity of pilot charts, which are predictive on the basis of averages within a range.

Colin Speedie

Hi Marc

that answer is yes, it does. In fact, I think it’s the seventh edition of World Cruising Routes that Jimmy is currently working on, and he tells me that many of the changes that have to be made relate directly to the new knowledge gleaned from their work on the Ocean Atlas.

And he made exactly the same point that you do in our conversation – the change is real, whatever the cause, and we’re all going to have to learn to deal with it. The simple, sad fact is that what is in effect, so far, a realtively minor inconvenience for us as cruisers represents something far, far more serious for the island communities affected – who may only be amongst the first to suffer.

Incidentally – the page selected from the Ocean Atlas for the article shows a major change in wind direction and speed for the traditional Pacific crossing from the ‘old’ pilot charts – which is why it was selected for this piece.

Best wishes


Marc Dacey

Thanks, Colin. I should sell my sixth edition before people grasp it’s out of date!

The funny thing is that I actually use pilot charts to give me guidance. Leaving Lake Ontario, we plan to “shake down” in domestic waters, and overwinter in Halifax or nearby, and hop, via a stop at St. John’s, to Ireland the next spring. So we are using the pilots to determine ice limits and prevailing winds for the first 450 NM part, followed by the 1,700 NM Atlantic run, which is probably a 14-20 day passage (I’m being conservative here: give me 25 knots off the port quarter and even our steel tank could do it in 11-12 days…but that’s not likely!)

Pilots are like mutual funds: past performance is no guarantee of future profits, and yet few serious sailors I’ve ever met do not consult them. If we accept that weather systems, currents and prevailing wind percentages *are* altering…and I do, particularly for certain latitudes…then we can weigh the last 20-30 years more favourably over 100 years ago as being more suggestive of trends in given parts of the ocean.

paul Mills

Hi Colin,

Very interesting reading – thanks as always. I wholeheartedly echo Dick’s comments above.

I also had a good nosey around the website, and it looks like a great trip ….. if only I could get away 🙁 On a separate note I was intrigued by the new completely unpainted boat and will certainly keep abreast of her build. There are certainly some influences of Boreal and I think Dashew evident.

The whole climate change issue is so difficult; for example I have been cruising Cornwall and the isles of Scilly for the past several weeks – the weather has been far better than recent years, and In have regularly swam for a hour or so without getting chilly!

One of those ‘small world things’ – the admin office for the whole project is less than a minutes walk from my training companies in Dursley, Glos…..: note to self, use other route for lunchtime sandwich run!


Colin Speedie

Hi Paul

Jimmy’s new boat is taking shape fast I understand – it’ll be good to see the final outcome.

And as I remarked above – it’s really the long term trends that matter with climate change – that’s where the facts seem to be found. But thank God that the South of the Uk has had a good(ish) summer at last!

Glad you liked the piece, and thanks for the compliments.

Kind regards


Nick Kats

Very useful post! I may get this book.

I’ve used the British Admiralty pilot chart for the North Atlantic about 4x, to plan out trips. I relied heavily on high probability to set general courses. All trips were 1500 to 3500 NM, round trip from west Ireland. In all 4 cases the winds were absurdly contrary to probability indicated by the chart. It was ludicrous. This leaves me uncertain about using this BA chart for future trips. Your article could be very timely!

Has anyone at AA used these books to plan trips? How did that work out? Looking for practical feedback here.

Thanks Colin.

Colin Speedie

Hi Nick

Like you, we’ve had our problems with the pilot charts, and I think it’s probably fair to say that they are now well overdue for review.

What Jimmy and Ivan have done is really good – and although I haven’t had the chance to use the new book for a future passage, out of interest I used them to review our transat this year in the light of their new evidence, and I’d have to say they were far closer to the reality of what we encountered than the old pilot charts.

Best wishes


John Kwiatkowski

This seems to explain quite a lot:
Looks like a lot more variability in seasonal weather patterns.

Colin Speedie

Hi John

Great links – thanks for sharing them with us.

Best wishes


Marc Dacey

People seem to have great difficulty with the concept that a) heat equals energy, and b) energy can increase the degree of oscillation, meaning that c) “climate change” can mean as much unseasonable cold (because there is energy to move cold from one place to another) as unseasonable warmth.

It’s not just an overall increase in heat, which is incremental over decades. It’s snow in July and sunburn in January, which kills crops bred to grow in less oscillating conditions.

Arctic ice didn’t melt as much this year, so “global warming” seems less credible. Snipers occasionally miss, too, but they still statistically hit their targets over time. I deeply regret that science has been in our culture replaced by judging the size of Kardashian buttocks and high scores in Angry Birds.

The effect of the breakdown in “seasonality”, for lack of a better term, is clear for the voyaging sailor: the pilots become less relevant and less accurate unless they reflect only that range of dates that produced the most current conditions.

John Lundin

Great article Colin,
Jimmy’s new project is significant given his depth of experience, and I’ll be following his progress. It’s in the spirit of what Mike Horn, Bjelke-Shapiro and the crew of Oceanwatch have undertaken in their seasoned prime.

The best climate information resource is It’s vitally important we allow the science community keep presenting their findings without interjecting arm-chair opinions. Mistaking immediate weather observations for climate patterns, is the most common way to steer the conversation off course.

There are some serious issues coming into focus, such as the alarming acceleration of melting being documented in Greenland and West Antarctica. These two behemoths were up until recently regarded as too big to fail, with most of the climate repercussions playing out in the sea ice and mountain glaciers around the world.

My wife recently completed her PhD in Glaciology at the University of Washington, working to improve climate chronologies. I’ve been fortunate to digest some of the science from her work and witness the depth of climate research that scientists are undertaking. Much can be learned with open ears.