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An international team of scientists and scholars have appealed to the United Nations for an international agreement on non-use of controversial climate change mitigation strategy known as solar geoengineering.

Promising, but...

Solar geoengineering, or solar radiation modification (SRM) is a proposed type of climate engineering which intends to limit the amount of sunlight that reaches the Earth and thereby lower global temperature. It is a sort of quick fix to reverse human-caused climate change. The technology involves practices like massive spraying of aerosols in the earth's stratosphere to block a part of incoming sunlight to cool the planet. There are other forms of solar radiation modification such as placing giant mirrors in space to reflect away Earth-bound sunlight, whitening rooftops and road surfaces, and lightening the colour of crop leaves through genetic modification.

Proponents of the technology cite that many climate models have consistently indicated that a moderate magnitude of solar geoengineering would bring important aspects of the climate average and extreme temperature, water availability, cyclone intensity-closer to their pre-industrial values, but opponents say that solar geoengineering deployment cannot be governed globally in a fair, inclusive and effective manner. For instance, deployment by one country could affect the weather patterns over others.

What could go wrong?

In an open letter, the initiators of the Solar Geoengineering Non-Use Agreement argue there are three main grounds for preventing the use of such technologies.

The unknown risk: They say the risks of solar geoengineering are poorly understood. There are uncertainties about the effects on weather patterns and agriculture.

Climate inaction by governments: The technologies could be used by governments or industries to delay their decarbonisation policies, carbon neutrality and other emission mitigating efforts

Who gets to decide?: Currently there is no global governance system to monitor or implement solar geoengineering schemes which could be set in motion today by a single country, or even a billionaire.

The letter goes on to call for five measures to be adhered to by the international community no public funding for solar geoengineering: no outdoor experiments no patents for solar geoengineering tech; no deployment of such tech and no support for solar geoengineering from international institutions.

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A new study published in journal Nature Food has found that persistently high levels of ozone pollution in Asia are costing China, Japan and South Korea an estimated $63 billion annually in lost rice, wheat and maize crops. The research used pollution monitoring data from the region and field experiments to show ozone affects Asia's crop yields more than previously thought.

The researchers found that on an average 33% of China's wheat crop is lost annually because of ozone pollution. While South Korea lost 28% of wheat. Japan lost 16%. For rice, the mean figure in China was 23%. In South Korea the figure was nearly 11%, while in Japan it was 5%. And maize crops in both China and South Korea were also affected. The crop is not grown in Japan in significant quantities. The study's authors said the findings should push policymakers to reduce emissions that produce ozone.

You may have learnt from your teachers that the ozone layer protects us from the harsh sunlight.

What is ozone?

Ozone is a highly reactive gas composed of three oxygen atoms-03. It occurs naturally in the stratosphere layer of the Earth's atmosphere. But ozone also comes from man-made sources and is found in the lowest layer of the atmosphere (troposphere). While the former affects life on Earth in positive ways, the latter does so in negative ways. Our concern in this article is the second form of ozone.

What is the ozone layer?

The atmosphere consists of a mixture of 78% nitrogen, 21% oxygen and 1% of other gases. Each of the five layers of our atmosphere has its own role in protecting Earth and supporting life on the planet. The second layer - the stratosphere - is the most stable region, where jets fly. It is also the region where ozone is abundant. Stratospheric ozone is formed naturally through the interaction of solar ultraviolet (UV) radiation with molecular oxygen (02). The layer, found about 10 to 40 km above the ground, is the ozone layer. It is part of the stratosphere and it protects life on Earth from the harmful effects of UV rays by absorbing them. Ultraviolet rays can damage DNA, and cause sunburn, skin cancer and cataract in humans.

What is ozone pollution?

At the ground level, ozone is a highly unstable and poisonous gas which is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). This happens when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight. When the percentage of ozone at ground level reaches alarmingly high levels, ozone pollution occurs. Ozone pollution is common in urban areas because of vehicular pollutions and industries, ozone can be transported long distances by wind so even rural areas, where farming lands are found, can also experience high ozone levels. A higher percentage of ozone gives rise to health issues such as chest pain, congestion and coughing. It also affects crops and other vegetation.

How does ozone affect crop yield?

Ozone damages crops by entering leaves during normal gas exchange. As a strong oxidant, ozone causes symptoms in crops such as yellowing, cell injury, spots, and reddening. Many factors such as soil moisture, presence of other air pollutants, insects or diseases, and other environmental stresses, can increase the impact.

Ozone is the key pollutant causing the yield loss of crops such as rice and maize. Wheat is the most sensitive when it comes to ozone-caused damage. Ozone exposure could have an even bigger impact on yields of soybean, peanut and cotton.

Why is this concern in Asia?

East Asia is one of the biggest bread baskets and ricebowls in the world. It supplies 90% of the world's rice and 44% of its wheat. The researchers said surface ozone is "posing a threat to food security."

Asia is also a hotspot for ozone. While ozone levels have declined in America and Europe over the last two decades, with the introduction of stricter air quality measures, the pollutant is increasing in Asia.

Further, industry, energy and urban expansion are competing for limited land resources.

What is the solution?

The best way to bring down ozone levels is to curb the use of fossil fuels - the same action needed to bring down greenhouse gas emissions causing climate change.

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Nitrous oxide, also known as laughing gas, is around 300 times stronger than carbon dioxide at heating the atmosphere. While its total emissions (6%) are less than those of carbon dioxide (76%) and methane (16%), nitrous oxide remains a powerful greenhouse gas that lingers in the atmosphere for around 114 years before disintegrating. Scientists at the Intergovernmental Panel on Climate Change (IPCC) estimate that three quarters of nitrous oxide emissions come from agriculture. Agricultural soil, especially because of the world's use of synthetic nitrogen fertiliser, is the principal culprit.

Nitrous oxide is not just a greenhouse gas, it is a very good indicator of a grower’s efficiency in his farming practices and how he manages the nitrogen he applies to his crop.

For every kilogram of nitrous oxide emitted, there are other nitrogen gases (e.g. di-nitrogen or N2) that are lost in far greater amounts, from 2-70 kilograms. These other gases have no impact on our atmosphere (which is already 78% di-nitrogen), but they are equivalent to lost production and ultimately lost income to a farmer.

Nitrogen fertiliser is not cheap. Every tonne of nitrogen costs the grower more than A$1,000, but it is critical for meeting the demands of a rapidly growing world population.

Australian farmers collectively apply nearly 1 million tonnes of nitrogen every year. If (conservatively) 25 kilograms is lost to the atmosphere for every tonne applied, that is $25 million dollars each year shaved off the economy.

Credit : The Conversation 

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