Cruising_World_2016-06-07

41

july/june 2016

cruisingworld.com

In the coming decades, what does climate change hold in store for cruising sailors? Leading

climate modeler and sailor Dr. Philip J. Rasch offers his take in a candid conversation.

BY PAUL VANDEVELDER

M

ore than any other

group I know, sailors

are keenly attuned

to the nuances of wind, waves,

tides, storms, calms, baromet-

ric pressure, clouds and tem-

perature. A new term in the

sailor’s glossary, climate change,

is going to be a factor in all

things sailing for the rest of our

lives and beyond.

A report released in

December 2013 by the

Intergovernmental Panel on

Climate Change predicted

an 8- to 10-degree F rise in

temperature by the end of

this century. For people who

pay attention to such things,

those numbers are alarming.

In matter-of-fact scientifi c

monotones, the atmospheric

physicists who wrote this new

assessment envision a world

much changed from the one we

know today, and their fi ndings

and predictions pose troubling

questions for long-distance

sailors: How is climate change

going to aff ect winds, ocean

currents and weather patterns

around the world? How is cli-

mate going to alter the way we

voyage across oceans in the

coming decades?

To get a real-world fi x on

answers to those questions,

I sat down with Dr. Philip J.

Rasch, a rock-star climate mod-

eler at the Pacifi c Northwest

National Laboratory in

Richland, Washington. I asked

Rasch — himself a sailor — to

explain in broad terms what we

can expect from climate change

in the near future.

PV: As you know, most blue-

water cruisers do their

open-water sailing in a

belt that girdles the globe

between 25 degrees N and 25

degrees S. What, if any, are

the changes in weather pat-

terns that climate models

see emerging as long-term

trends in tropical and sub-

tropical waters?

Rasch: There are many dif-

ferent ways to answer that

question. Over the last cen-

tury we’ve seen ambiguities

in wind and wave patterns

around the globe, and for the

purposes of understanding

how climate is infl uencing

those circulation patterns,

it’s not helpful to isolate the

tropics from the midlatitudes,

or the midlatitudes from the

higher latitudes. They’re all

tied together. That said, there

are clear signals, or signatures,

for strengthening wind speeds

in some regions and diminish-

ing wind speeds in others. In

the tropical zone, storms are

increasing in strength, but it’s

unclear yet whether they’re

increasing in frequency.

Related to that, another sig-

nature that seems to be robust

is changes in wave height in

the midlatitudes of the Pacifi c

and Atlantic. This may be

infl uenced by a climate fea-

ture near the equator called

the intertropical convergence

zone. This zone seems to have

shifted southward over the last

THE Climate CONUNDRUM

ISTOCKPHOTO (TOP); COURTESY OF PHILIP RASCH

Green Wakes

Malé, the capital of the

Maldives, is home to more

than 125,000 residents and

is a popular stopover for

cruisers crossing the Indi-

an Ocean (left). The island

nation is the lowest in the

world and has a high risk of

being submerged due to ris-

ing sea levels. Dr. Philip J.

Rasch (below) is a sailor and

climate scientist with some

sobering predictions.