Climate riddles

Published on June 12, 2016.

Male is the capital of the Maldives, home to more than 125,000 locals and a popular destination for many sailors crossing the Indian Ocean. These islands are located just above sea level and are very likely to be flooded due to rising sea levels.

Main Capital of Maldvies, Male. Picture taken from air.

Yachtsmen are much more interested in such concepts than other people as: - wind, waves, tide, storm, calm, barometric pressure, cloudiness and temperature. In the vocabulary of yachtsmen, there is also such a concept as - climate change, this factor will have a decisive impact on yachting until the end of their lives and further in the future.

According to the report of the intergovernmental expert group on climate change, published in December 2013, the average annual temperature on our planet will rise by 8-10 degrees Fahrenheit or 4-5 degrees Celsius (you can see in detail how the temperature values are recalculated at this link http://www.fahrenheit-celsius.info/) For those people who pay attention to such publications, this is a warning signal. Experts in the physical processes occurring in the atmosphere predict that the whole world will change significantly compared to what we see today, their scientific discoveries and forecasts already pose a number of unusual questions for yachtsmen who travel long distances: How will climate change affect winds, oceanic currents and weather maps around the globe? How we will be crossing oceans in the future thanks to climate change. In order to get the most reliable answers to these questions, I turned to Philip Rush, a rock star in the field of climate change modeling, Ph.D., Pacific Northwest Laboratory, Richland, Washington.

PV (Paul VanDevelder): - Nowadays, as you know, the vast majority of yachtsmen who travel long distances cross the oceans along a wide strip from the 25th parallel of the northern hemisphere to the 25th parallel of the southern hemisphere. What will happen to the weather in these latitudes in the near future and in the longer term?

Rasch: There are many different answers to your questions. Over the last century of meteorological observations, we have seen uncertainty in the winds and in the direction of waves around the globe, and in order to understand how climate change affects the prevailing winds and waves, we cannot consider tropical latitudes separately from temperate latitudes and closer to the poles. They are all related. It can be said unequivocally that there are signs of a significant increase in wind speed in one area and a weakening of winds in another. In the tropics, storms have become much more powerful, but at the same time it cannot be said that they have become more frequent.

In this regard, there is a significant increase in wave height in the middle latitudes of the Pacific and Atlantic oceans. The wave height is also influenced by such a phenomenon near the equator as a zone of tropical convergence. (this is a narrow strip near the equator where the northern and southern air masses converge, as a rule, a low atmospheric pressure is created in this zone) So, over the last century, this zone has shifted to the south. This displacement determines where the greatest amount of atmospheric precipitation will fall, where exactly on land the rain will fall along which path the cyclones will pass. Whether you are a farmer in Africa or fishing in the Atlantic or sailing in this region, all of these have a serious impact on you.

PV: We are seeing some unexpected changes in the climate model such as winds in the tropics and subtropics becoming weaker and at the same time the prevailing winds (trade winds) are increasing in speed. Why is this happening?

Rasch: When we talk about the influence of climate on the weather, it is necessary to understand how wind and currents distribute heat throughout the planet.

More and more heat falls on the equatorial regions and this energy is then distributed throughout the planet by wind and ocean currents. The polar regions reflect some of the heat back into space. Winds carry equatorial heat to the poles, along with greenhouse gases, all of this circulation determining the planet's climate for many centuries in a row.

We note a slowdown in circulation processes in tropical areas as well as a decrease in wind speed. Some eddies move to the north or south, others go to the west or east, heat also seeps into the depths of the ocean, a gradual increase in water temperature occurs, all this together spreads heat around the planet. Currently, all these heat fluxes are in a state of uncertainty and constant change.

PV: What about the occurrence of hurricanes like Hurricanes El Niño and La Niña?

Rasch: Our calculations show that such hurricanes will be even more powerful. We also predict that Hurricane El Niño's southern footprint will move further east. The increase in ocean warming will move the hurricane's impact zone and make it more violent, as a result, we will observe more destruction and negative consequences. At the same time, countries such as Chile and Peru have benefited greatly from the cold body of water from the depths bringing in huge amounts of food for fish, which has a positive effect on the entire fishing industry in the region. Small changes in ocean currents and temperatures have a huge impact on the lives of fishermen downstream. Ichthyologists throughout the Southern Hemisphere are very concerned about these phenomena, because many people in Africa and South America eat fish.

This map shows sea surface temperature anomalies in August 2015. Areas that are 5 degrees Celsius warmer than usual at this time of year are highlighted in dark red.

PV: You've already said that many yachtsmen tend to only notice what is happening at sea without taking into account the phenomenal changes that are taking place on the ground. Could you tell us more about these changes?

Rusch: We see a good example of this influence in Africa.

As I said before, as a result of the displacement of the tropical convergence zone (the meeting point of northern and southern air masses), the zone of tropical rainfall has shifted. The zone between the Sahara Desert and the savannah has become much wider and drier. Due to this, the zone of formation of tropical cyclones over the ocean has shifted to the east. A small change in the climate on the mainland makes a much larger change in the processes that occur over the oceans.

PV: Lately, has there been more speculation about how climate change is affecting the severity and frequency of major storms?

Rusch: Let me point out that a lot of people are concerned about the changes that are associated with surface currents such as the Gulf Stream in the Atlantic Ocean and the current of Curacao in the Pacific. These warm rivers in the ocean carry heat away from the equatorial regions, north to the poles. It is very interesting for us to understand in more detail how these currents affect the formation of storms and the distribution of heat in the Northwest Pacific and Northern Europe.

These are very complex systems. Warmed water rushes north, while in the other part of the ocean, cold water from the north rushes south to the equatorial region. This water cycle has been occurring for centuries and has the greatest impact on ocean temperature and, as a consequence, on the formation of storms. The warmer the water rushes north, the more violent the storm will be formed as a result of the movement of this amount of energy.

We call it reverse meridian circulation.

(meridional overturning circulation, or MOC), most people have never heard of this, but these are very important processes that are affecting the increasingly rapid melting of ice in Antarctica and the Arctic including Greenland.

PV: What is it that the process of melting ice in Greenland affects the formation of storms in the tropics?

Rasch: Yes, exactly, this is already happening at the present time. It is worth taking a close look at the paths of storms across the planet. They are all different but in general, they move closer to the poles. Since they pass closer to the poles in constantly changing wind flows, the amplitude of the storms will also be different.

PV: If you are planning a long family sailing trip, what climate change will have the biggest impact on it?

Rusch: As the planet continues to heat up, we expect the waves in mid-latitudes to be higher and higher. Tropical cyclones and hurricanes will become more intense. Those places on the planet that were wet will be more and more humid and those places that have suffered from drought will be even drier. Ten years ago, the IPCC (Intergovermental Panel of Climate Change), the International Commission for the Study of Climate Change, reported that one should not fear a possible catastrophic rise in ocean levels. But this level up is already happening. This speaks to how quickly change is taking place. The more ice melts in the polar regions, the more the water level in the world's oceans rises and it expands. We thought that the low island groups in the Indian Ocean were safe for at least the end of the century, this is no longer the case. The Maldives will be under water in the next few decades.

PV: This is a very sobering prediction.

Rasch: Yes it is. We are all in a region of the unknown when it comes to climate.

Paul VanDevelder has been traveling the Pacific Ocean along the Northwest Coast of the United States for many years and is a frequent contributor to the environment and natural resources for the Los Angeles Times and the New York Times.

09.07.2016