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5 June, 2018 11:20:57 AM
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The 5th June: World Environment Day

The sun’s total energy output varies on multiple cycles and is related to the number of sunspots, with slightly higher temperatures when there are more sunspots, and vice versa
Mohammed Abul Kalam, PhD
The 5th June: World Environment Day

It’s time! Once again UN Environment seeks to make the biggest global call and mobilization for action on 5 June, World Environment Day (WED). World Environment Day is the biggest annual event for positive environmental action and takes place every 5 June. This year’s host country Canada got to choose the theme and will be at the centre of celebrations around the planet.
World Environment Day, which is this year hosted by Canada, is the biggest annual event for positive environmental action and takes place every 5 June. Since it began in 1972, global citizens have organized many thousands of events, from neighbourhood clean-ups, to action against wildlife crime, to replanting forests. "Connecting People to Nature", the theme for World Environment Day 2017, implored us to get outdoors and into nature, to appreciate its beauty and its importance, and to take forward the call to protect the Earth that we share. Last year’s theme invited us all to think about how we are part of nature and how intimately we depend on it. It challenged us to find fun and exciting ways to experience and cherish this vital relationship.
Many areas in the capital and its suburbs became waterlogged following three hours of downpour yesterday (Wednesday) morning, causing traffic snarls. Similar reports also came from Demra and Narayanganj, 12 km south of Dhaka. Met Office sources said they recorded 52mm of rainfall in the city between 9am and 12 noon. People had a tough time negotiating waterlogged streets and traffic stood standstill. Abdur Rahman, a meteorologist at the Dhaka Met Office, said such snap rain would end in the next couple of days. But it would not be all over. There could be drizzles and light rain, but not so much to cause inconvenience. Meteorologists have been talking about the unusual behaviour of the weather in May, usually considered a dry month (The Independent, May 24, 2018).

Extreme weather and temperatures grounded around the globe.It feels as if Bangladesh has had all manner of extreme weather events in 2017. We had severe heat at both the end and start of the year. Casting our minds back to last summer, experienced our hottest summers and rainfalls endured extended periods of very high temperatures.

Overall 2017 was the warmest non-E1 Nino year on record globally, and over the past 12 months we have seen plenty of extreme weather, both here in Bangladesh and across the world. Here I’ll round up some of this year’s wild weather, and look forward to 2018 to see what’s around the corner. Elsewhere in the world there was plenty more headline-worthy weather.

Hurricane after hurricane after hurricane…The Atlantic Ocean had a particularly active hurricane season, with several intense systems. Hurricane Harvey struck Texas and its slow trajectory resulted in record-breaking rainfall over Houston and neighbouring areas.

Then Hurricanes Irma and Maria, both of which reached the strongest Category 5 status, brought severe weather to the Caribbean and southeastern United States just a couple of weeks apart. Island nations and territories in the region are still recovering from the devastation.

Around the same time, the Indian subcontinent experienced a particularly wet monsoon season. Flooding in India, Pakistan, Bangladesh, and Nepal killed more than 1,000 people and affected tens of millions more.

In many cases, especially for heat extremes, we can rapidly identify a human influence and show that climate change is increasing the frequency and intensity of such events. For other weather types, like the very active hurricane season and other extreme rain or drought events, it is harder (but not always impossible) to work out whether it bears the fingerprint of climate change.

Under the Paris Agreement, the world’s nations are aiming to limit global warming to below 2℃ above pre-industrial levels, with another more ambitious goal of 1.5℃ as well. These targets are designed to prevent the worst potential impacts of climate change. We are currently at around 1℃ of global warming.

Even if global warming is limited to either of these levels, we would see more winter warmth like 2017. In fact, under the 2℃ target, we would likely see these winters occurring in more than 50% of years. The record-setting heat of today would be roughly the average climate of a 2℃ warmed world.

While many people will have enjoyed the unusual winter warmth, it poses risks for the future. Many farmers are struggling with the lack of reliable rainfall, and bad bushfire conditions are forecast for the coming months. More winters like this in the future will not be welcomed by those who have to deal with the consequences.  Over the past few days there has been a lot of talk about the Paris climate agreement, from which the United States has withdrawn. Although this is a setback, there is still complete consensus from the world’s governments that a strong effort to tackle climate change is needed.

The Paris Agreement aims to limit global warming relative to a pre-industrial baseline. Its precise commitment is:Holding the increase in the global average temperature to well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃ above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.

But this begs the question: what are “pre-industrial levels”?Clearly, if we’re aiming to limit global warming to 1.5℃ or 2℃ above a certain point, we need a common understanding of what we’re working from. But the Paris Agreement doesn’t provide a definition.

This becomes key as governments expect climate scientists to coherently compare different plans to reach their Paris targets. It’s crucial to be clear on what researchers mean when we say “pre-industrial”, and what assumptions our projections are based on.Of course, as the chart below shows, no matter which baseline we use it’s clear there’s been a drastic rise in global temperature over the last century. Global temperatures are on the rise and are about 1℃ above late 19th century levels.

The Industrial Revolution began in the late 1700s in Britain, and spread around the world. But this only marked the beginning of a gradual rise in our greenhouse gas emissions. Various studies have found climate change signals appearing on a global scale as early as the 1830s, or as recently as the 1930s.

Besides the evolving and increasing human influence on the climate, we also know that plenty of other natural factors can affect Earth’s temperature. This natural variability in the climate makes it harder to determine a single precise pre-industrial baseline.Scientists separate these natural influences on the climate into two groups: internal and externalforcing.

Internal forcing transfer heat between different parts of Earth’s climate system is The El Nino-Southern Oscillation, for example, moves heat between the atmosphere and the ocean, causing year-to-year variations in global average surface temperatures of about 0.2℃. Similar variations also happen on decadal timescales, which are associated with slower energy transfers and longer variations in Earth’s temperature.

External forcing comes from outside Earth’s climate system to influence global temperature. One example of an external forcing is volcanic eruption which sends particles into the upper atmosphere. This prevents energy from the Sun reaching Earth’s surface, and leads to a temporary cooling.

Another external influence on Earth’s climate is the variability in the amount of energy the Sun emits. The Sun’s total energy output varies on multiple cycles and is related to the number of sunspots, with slightly higher temperatures when there are more sunspots, and vice versa.

Earth has experienced extended periods of cooling due to more frequent explosive volcanic eruptions and periods of few sunspots – such as during the “Little Ice Age”” which lasted roughly from 1300 to the 1800s.

There is high variability in the solar and volcanic influences on the climate (top row) while greenhouse gas influences rise over time (bottom row). A suggested 1720-1800 baseline is highlighted in grey.

All of these factors mean that Earth’s climate can vary quite substantially even without human interference.It also means that if we choose a pre-industrial baseline when there was low solar activity, like the late 1600s, or in a period of high volcanic activity, like the 1810s or the 1880s, then we would have a lower reference point and we would pass through 1.5℃ or 2℃ sooner.

But scientists are defining “pre-industrial” or “natural” climate in different ways. Some work from the beginning of global temperature records in the late 19th Century, while others use climate model simulations that exclude human influences over a more recent period. One recent study suggested that the best baseline might be 1720-1800.These different definitions make it harder to synthesize the results from individual studies, which is vital to informing decision-making.

This will have to be a consideration in the writing of the IPCC’s report, as policymakers will need to easily compare impacts at different levels of global warming. There is no definitive way to determine the best “pre-industrial” reference point. An alternative might be to avoid the pre-industrial baseline altogether and instead set targets from more recent periods, when we have a better grasp of what the global climate looked like.

On December 12, 2015 in Paris, the United Nations Framework Convention on Climate Change finally came to a landmark agreement.Signed by 196 nations, the Paris Agreement is the first comprehensive global treaty to combat climate change, and will follow on from the Kyoto Protocol when it ends in 2020. It will enter into force once it is ratified by at least 55 countries, covering at least 55% of global greenhouse gas emissions.

What’s in store for 2018?The main problem when trying to offer an outlook is that extreme weather is hard to predict, even on the scale of days or weeks in advance, let alone months. The La Niña is also likely to mean that 2018 won’t be a record hot year for the globe. But it’s a safe bet that despite the La Niña, 2018 will still end up among the warmest years on record, alongside every other year of century. Rising global average temperatures, along with our understanding of the effect of greenhouse gas emissions, are one of our clearest lines of evidence for human-caused climate change.

So it’s hard to say much about what extreme weather we’ll experience in 2018, other than to say that there’s likely to be plenty more weather news to wrap up in a year’s time.

The writer is former Head, Department of Medical Sociology,

Institute of Epidemiology, Disease Control & Research (IEDCR)

Dhaka, Bangladesh E-mail: med_sociology_iedcr@yahoo.com

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Editor : M. Shamsur Rahman
Published by the Editor on behalf of Independent Publications Limited at Media Printers, 446/H, Tejgaon I/A, Dhaka-1215.
Editorial, News & Commercial Offices : Beximco Media Complex, 149-150 Tejgaon I/A, Dhaka-1208, Bangladesh. GPO Box No. 934, Dhaka-1000.

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