Winds and waves on the oceans are (slightly) stronger each year

In the world of climate science – and science in general – the data is king. The more you have and the higher the quality, the better. And while trends such as rising sea levels and temperatures are based on impeccable data, not all measures of climate change have been so successful.

Take the example of the global climate of winds and waves, which measures trends in wind speed and wave height in the oceans around the world. These two factors affect the interaction between the atmosphere and the oceans of energy and carbon (more winds are equal in choppy waters, which can hinder air-water energy transfers), and of course, waves higher could cause more problems during the day. Storm surges and affect flood levels. But it was historically difficult to obtain reliable long-term data on these phenomena in order to study any possible trend.

Until now, that's it. A paper in Science uses satellite data today to analyze wind speed and wave height over 30 years and has concluded that both are increasing, particularly in the southern hemisphere, and particularly in the southern hemisphere. extreme conditions like storms. They have also demonstrated a useful way to study these things in the first place, which should prove useful for scientists who are going from the front.

Defective data

Why has it taken so far to collect and analyze what should be a fairly simple data set? As the authors of the paper explain, it was not so easy. Ocean buoys, "the most obvious data source," have proven problematic, as their construction and instrumentation have changed over the years, which means that the data they have created is not really consistent in the long run. term. It would be a question of comparing apples with, if not oranges, at least other types of apples – it is not ideal.

So, they turned to satellite recording, which is currently extending from 1985 to 2018. Not bad, but the same concerns were also expressed: with all types of hardware and software used in the Space, their data may not be sufficiently reliable. for such a research either?

The authors therefore decided to inquire. As you may have guessed, it worked.

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In particular, they studied the data collected by three types of instruments embedded on satellites: altimeters, which measure both the height of the waves and the speed of the wind; radiometers, which measure the wind speed; and scatterometers, which measure wind speed and direction.

After verifying all the figures, carrying out cross-validations with other satellites and simply making sure that they did not let themselves be fooled, the authors concluded that the previous 30 years had been marked by a strong positive trend of the speed of the wind in the world. a smaller (but still noticeable) increase in wave height. They also noted that the trends were much stronger in extreme cases, which they defined as the data of the 90 series^th percentile.

Not that any of the actual changes were particularly high. The wind speed increased about one inch per second each year, about twice the speed of a garden snail, in the Southern Ocean and south of the equator, where the trends were the strongest. The change was about half that of the North Atlantic. (The extreme cases had the same distribution, but with faster speeds, about two inches per second per year.) The wave height was not as sharp, but there were plates with overall increases of about one tenth of an inch per second. year, and a surprising place in the North Pacific with a drop of about half an inch a year.

Close the climate

This may not seem like a lot, inch fractions here or there, but the results clearly show trends for overall behavior over time. The authors point out that any improvement in our understanding of the global climate of winds and waves is helpful because "estimates of future states of winds and waves in the ocean, and of changing extreme conditions, are important elements of the projections of the total level of the sea ".

The team also showed that satellites could be trusted because each of the different types of instruments aboard 31 satellites in total orbit finally showed consistent data between them. This means that future studies will be able to rely on this richer and richer dataset without having to worry about comparing apples to anything else.

Thus, not only did the authors add specific elements of these extremely important data to the global climate register, but they also facilitated the task of future researchers.