Global Dimming is a recent phenomenon that questions all our thoughts on how best to protect the planet by reducing air borne particulates in the atmosphere.

Scientists have found that the amount of sunlight reaching the Earth’s surface has drastically declined over the last 5 decades. This in turn has actually had a cooling effect on the Earth. Recent initiatives to reduce pollution and particulate emissions have started to have a positive impact and reduce Global Dimming – leading to a possible acceleration in Global Warming.

An English scientist working in Israel in the 1950’s coined the term ‘Global Dimming’. Dr. Gerald Stanhill was given the task of measuring how strongly the sun shone over Israel to help with the designs of an irrigation scheme. 20 years later he went back to repeat his measurements to check they were still valid. The results he found were astonishing. In 30 years the amount of sunlight reaching the earth surface had dropped by 22%.

The findings shocked the scientific world and so the idea was dismissed. Dr. Stanhill decided to investigate further. He found that another scientist in Germany has also recorded a reduction in the sunlight over the Bavarian Alps. Dr. Beate Liepert and Stanhill researched the phenomenon and found the same story to be true worldwide. In Antarctica, solar energy had dropped by 9%, 10% in the US, and by nearly 30% in Russia.

But the focus has been on Global Warming and the amount of carbon dioxide we produce leading to the Greenhouse Effect and the general thought that the Earth was heating up. It wasn’t until two Australian scientists, using a different method to record solar energy, found the same to be true, that the world’s meteorologists started to pay attention.

But what was causing it? Scientists knew that it wasn’t the sun so it had to be something here on earth. It was a study by Veerabhadran Ramanathan that began to unravel the mystery.

Veerabhadran noticed declining sunlight over large areas of the Pacific Ocean in the mid-1990s. But it was his study on the Maldives that gave him the answer. He knew that the sun had to pass through the earth’s atmosphere to reach the surface so the problem must lie there. He knew that there was one strong suspect – Pollution.

Almost everything we do to create energy causes pollution. Burning fossil fuels and wood, whether in cars, power plants or in the home doesn’t just produce invisible greenhouse gases, it also produces visible pollution. Tiny airborne particles of soot, ash, sulphur compounds and other particles are produced.

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He decided to test his theory in the Maldives. The Maldives is made up of a string of Islands and it is only the Southern ones that enjoy clean air. The Northern islands rest in a stream of polluted air that descends from India. He and his colleagues decided to compare the two.

His findings were astonishing. A pollutant layer 3 kilometres thick reduced sunlight reaching the ocean by 10%. Existing models assessed that the human effects to be in the range of 0.5-1%, so their discovery was tenfold higher.

The study showed that the airborne particles were blocking some of the sunlight themselves, but more detrimental was the impact they were having on cloud formations. The airborne particles were turning them into large reflective mirrors. The optical properties of clouds were changed by the man-made particles around which the water droplets form. Polluted clouds contain a greater number of water droplets each one a lot smaller than “unpolluted” clouds. Lots of smaller droplets reflect more sunlight than fewer big ones, therefore preventing the heat and light of the sun getting through.

Scientists around the world now believe that “Dimming”, by reducing the full power of the sun from the oceans, is disrupting the equilibrium of the Earth’s water cycle.

It has been suggested that it is Dimming that caused the droughts in Ethiopia in the 1970’s and 80’s. Across the region known as the Sahel, it is the monsoon rains that help give the soil life to grow crops. However, during that time the rain belt failed to shift northwards. It is suggested that the pollution from Europe and America that blew across the Atlantic, affected the clouds properties. This in turn prevented the oceans north of the equator from warming up, and hindering the northward shift of the rain belt that normally supplies the Sahel.

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But there could be more tragic consequences as Professor Veerabhadran Ramanathan explained, “My main concern is this air pollution and the Global Dimming will also have a detrimental impact on the Asian monsoon. We are not talking about few millions of people, we are talking about few billions of people.”

However, the scariest aspect of Global Dimming is that scientists may have underestimated the effects of the greenhouse effect and Global Warming. Scientists know that the extra carbon dioxide we have placed in the atmosphere has resulted in a temperature rise of only 0.6oC. In the Ice Age, the same level of CO2 would cause a 6oC rise, so something must be having a cooling effect – Global Dimming.

It was a climate scientist called David Travis, on his way to work in Madison Wisconsin, who first caught a glimpse of what the world would be like without Global Dimming. On September 12th 2001, as America mourned the aftermath of the tragedy, 800 miles away David was driving to work and noticed that the skies were unusually bright and clear.

For 15 years David Travis had been studying the effect that vapour trails left behind from high-flying aircrafts had on the sky. Though each individual contrail looks small, when there are hundreds spread out over the sky they can cover for example, 50-70% of the west coast of America.

The problem he faced was how to test how the effect the vapour trails were having on the skies. He had to find a day when there were no flights but of course that would be impossible until the tragic events on 11th September 2001 took place. For three days after the tragedy, all commercial aircraft in the US had been grounded. It presented Travis with the perfect opportunity to complete his theory.

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He set about collecting data from over 5000 weather stations across 48 States. He focused on the temperature range for each day instead of just the temperature, which varies a lot from day to day. The study showed that during the grounding the temperature jumped by over 1oC, which was the largest swing in temperature change in over 30 years.

“The 9/11 study showed that if you remove a contributor to Global Dimming, jet contrails, just for a three day period, we see an immediate response of the surface temperature. Do the same thing globally we might see a large scale increase in global warming”, explained Dr David Travis.

That is where we get ourselves into a ‘catch-22’ situation. If you solve the problem of Global Dimming, by reducing airborne particulate pollution and cleaning up the atmosphere, the Earth is going to get considerably hotter. It is believed that this is not just theory, the European Directive to cut air pollution has seen clearer skies and a reduction in Dimming, but with it European temperatures have started to rise, noticeably the unbearable summer of 2003.

So what it boils down to is that while the Greenhouse effect has been warming up the planet, Global Dimming has been keeping it cool. The warming caused by CO2 has been hidden from us by the cooling from air pollution.

At present, our future predictions of CO2 levels look set to rise sharply over the coming decades, but particle pollution is being brought under control – especially in the Western World.

Dr Peter Cox, from the Hadley Centre Met Office said, “We’ve got two competing effects really, we’ve got the greenhouse effect, which has tended to warm up the climate. But then we’ve got this other effect that is much stronger then we thought, which is a cooling effect that comes from particles in the atmosphere. And they are competing with one another…if it turns out that cooling is stronger then we thought then warming also is a lot stronger then we thought, and that means that the climate is more sensitive to carbon dioxide than we originally thought, and it means that our models may be under sensitive to carbon dioxide”.

Current climate models predict a warming of 5 degrees Celsius by the end of the century. But Cox and his colleagues believe that temperatures could rise twice as fast causing irreversible damage in as little as 25 years.

“If we don’t do anything by 2030, we could have Global Warming exceeding two degrees, and at that point it’s believed the Greenland ice sheet would melt in a way that you wouldn’t be able to stop it once it started. It would lead to a sea level rise of seven or eight metres”, added Dr Cox.

Dr Cox’s calculates that the world could be ten degrees warmer in just under a century rendering many countries uninhabitable. And just when you thought things couldn’t get any worse, there is a greenhouse gas eight times stronger then carbon dioxide that could be leashed into the atmosphere.

The rising temperatures are in danger of destabilising a natural store called Methane Hydrate, which is stored in a “frozen” form at the bottom of the ocean.

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So what can we (the industrial gas companies) do?

Industrial gas companies have been assisting the aims of most countries to reduce particulate pollution. Examples include involvement in the Cleaner Fuel initiative – using Hydrogen to cut down or eliminate sulphur from transport and heating fuels and hence reduce the SOx emissions. Industrial gases, namely oxygen, has been used to reduce NOx emissions in chemical and combustion processes. Industrial Gas companies have and continue to develop applications using industrial gases to reduce both emissions and VOCs (Volatile Organic Compounds).

The above has helped to reduce airborne pollution but a lot still has to be done however, progress is being made. Everyone knows this makes sense but the result is lowering Global Dimming and hence “releasing” the more devastating effect of Global Warming.

The only way forward is to also focus on the root causes of Global Warming.
The Kyoto protocol on climate change, which today became legally binding, aims to cut CO2 emissions in developed countries by 5.2% below 1990 levels, by 2012. 141 countries that account for around 55% of greenhouse gas emissions. However, the US and Australia have abstained for economic reasons, and developing countries such as China and India are outside its framework.

Is there a role for industrial gas companies? Can they use their 100+ years of industrial gas technology development to assist in reducing the production of gases causing global warming – such as CO2 and Methane.

BOC said, “Climate change is now recognised as a significant environmental issue. This presents [us] with challenges and opportunities. The most significant challenge is that [we] are a major energy user and a partner and supplier of products to energy intensive industries such as iron and steel. Opportunities lie in the development of products and services that help customers manage their own climate change issues, for example, energy efficiency improvements or cleaner production that reduces greenhouse gases.”

One area the industrial gas companies are involved in is the use of more environmentally acceptable refrigerant gases. Freon (an ozone degenerating gas) was commonly used in refrigerators, air conditioning and even blowing agents. More environmentally friendly products have slowly replaced these – with industrial gas companies playing an increasingly important role in this process. BOC said, “For example, due to the rapid growth in worldwide demand for natural refrigerants, the distribution of our range of hydrocarbons was extended to the Philippines, Malaysia and Thailand this year. East Asia is a key market for air conditioning and refrigeration with users eager to extend their range of solutions that minimise industry’s contribution to global warming.”

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Industrial gas companies remain at the forefront of cleaner fuels. The use of Hydrogen in automobiles has been headlines in recent years (combustion results in water vapour emissions not CO2). Several of the major industrial gas companies are now playing a role in promoting the Hydrogen Economy – For example Praxair, along with the support of DaimlerChrysler and BP, have recently introduced their first Hydrogen refilling station at Los Angeles International Airport in California. Linde has one in Munich and BOC and Air Products have all participated in Hydrogen Fuelling projects. Linde have organised their second ‘International Hydrogen Day’ in Berlin for February 24th.

We are a long way off the “ideal” of a true Hydrogen Economy – but the green shoots of this increasingly important sector will hopefully be accelerated by Governments and company’s involvement – such as the industrial gas companies so that the Earth will remain green and not go the way some scientists are predicting within this Century.