Grew in Power over
much of the Oceans
Waves now more Frequent in Temperate Zones
|Coast Guard boat climbs a breaking
wave at Columbia River bar. CREDIT:
NOAA Photo Library
scientists conclude that winds have increased by 5 to 10%
in velocity over the world's oceans during the last 17 years,
and that extreme winds (the top one percent of wind speed
values) have increased in speed even more than the average
winds have. Reporting in the April 22
Science, the three scientists I. R. Young,
S. Zieger and A. Babanin of Swinburne University in Melbourne
used perhaps the most accurate tool now available, radar
altimeters on board the GEOSAT satellites, to map winds
and waves over the oceans. The most extreme winds are now
15% stronger over nearly all areas of the ocean.
are pushed along by the winds, so it is not surprising that
wave heights have also increased over many areas. The relationship
is more complex, however, as long-period "sea swell"
originates in faraway storms, while local waves are caused
by local winds. Where a crest of swell meets a local wave
crest, the two waves add such that a high mound of water
appears. So average and maximum wave heights are related
not just to the strength of the local wind, but also to
the power and duration of distant storms. The 23-year trend
in wave heights is not as significant nor as easy to explain
as the upward trend in wind speeds; in fact, there is no
trend for monthly-average wave heights. But the most extreme
waves (the top 1% of wave heights) have increased in height,
and the increase is statistically significant. Height of
these large waves grew by 10% over 20 years (satellites
have measured the trend for 23 years), in the temperate
latitudes of the oceans, from latitudes 35° to 60°
in both Northern and Southern hemispheres.
Waves have apparently
not grown in most of the Tropical oceans, even though wind
speeds have increased on average in the Tropics. In these
regions, sea swell affects the wave regime more than locally
generated winds do.
findings support the work of Oregon’s Peter Ruggiero,
who looked at data from two offshore buoys in the Pacific
Ocean 250 miles west of that state. The buoys reported an
18% increase in significant wave height during the 30 years
ending in 2007. (The term “significant waves”
refers to the highest one-third of all observed waves.)
Ruggiero did not examine the causes for the shift in Pacific
But the Intergovernmental Panel on Climate Change (IPCC)
did look at causes that now explain the stronger winds that
the Australians found and the stronger waves that both groups
found. IPCC scientists documented lower surface air pressure
in the Bering Sea and the Arctic Ocean, plus higher air
pressure in the subtropical belt, plus a northward shift
in the same belt of high pressure. Together, these changes
would strengthen the winds over the North Pacific Ocean.
The IPCC found the greatest wave size increases in the northeast
Pacific Ocean near North America. They considered it likely
that the shifts in the pressure pattern were due in part
to human influence. We may conclude that the changing wind
and wave climate of the oceans is another human influence.
Trends in Wind Speed and Wave Height
” by I.R. Young,
S. Zieger, and A.V. Babanin (2011). Science
, v. 332,
22 April 2011, p. 451–455.
wave heights and extreme-value projections: the wave climate
of the U.S. Pacific Northwest” by Peter Ruggiero,
P.D. Komar, and J.C. Allen (2010). Coastal Engineering,
v. 57, May 2010, p. 539-552.
A Fortune, Ph.D.
climate-science dot org
at Corvallis, Oregon, USA
Hot Summers of 2003/2010 break 500-year record
of the central and eastern two-thirds of the USA is now in
the grip of a pronounced heat wave, as of this July. How often
has it been exceptionally warm in the first years of the twenty-first
century? According to scientists from four European nations,
the hot summers of 2010 and 2003 likely exceeded the warmth of any other summer in the last 500 years in one-half of Europe. Their conclusion
appeared in the 8 April, 2011 issue
of Science ( note, below).
heat wave of 2003 was responsible for about 70,000 heat-related
deaths in central and western Europe (mainly in France). And last
year, well-populated western Russia and surrounding
countries like the Ukraine and Finland roasted. Some 55,000
people died in Russia from the heat. That country suffered
economic losses of $15 billion, or about 1% of its gross domestic
product, from numerous wildfires and crop failures. The intensity
and extent of the 2010 heat wave surpassed the 2003
Does last year’s
heat wave in Russia stand out in the historical record?
European scientists looked at both historical climate records
and “proxy” records from sediments, tree rings
and other clues since the year 1500. They found that temperatures
in the past ten years surpassed those in any other decade
since 1500. In other words, the 2003 and 2010 summers were likely hotter than any in the five centuries up to 2000. In
the last ten years, the area of Europe that has ever had a
summer warmer than 99% of the summers in the 30-year period
from 1971 to 2000 has doubled. There may be other clever ways
that statisticians can say this; but recent summers have been
the summer climate of Europe be influenced by global warming?
The authors reviewed climate model experiments and concluded
that a summer like 2003 is projected to occur again by mid-century
(2050), but not a summer as warm as 2010. However, by the
year 2100, a summer like 2010 may occur roughly every eight
years in Eastern Europe.
Hot Summer of 2010: Redrawing the Temperature Record Map of
Europe” by David Barriopedro,
E.M. Fischer, J. Luterbacher, R.M. Trigo, and R. Garcia-Herrera.
Science, vol. 332, 8 Apr. 2011, 220–224.