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I often find people using the terms weather and climate interchangeably - this creates much confusion, and makes any serious discussion of the important subject of climate change (CC) very difficult. The media, political leaders, industries with vested interests have conveniently exploited this confusion.
Both weather and climate describe certain properties of the atmosphere - like temperature, wind speed and direction, humidity, rainfall etc. The difference between weather and climate is that
weather describes the atmospheric conditions at a particular time and location, while
climate is the averaged atmospheric conditions of a region over a period of time (normally 30 years or more).
Weather in London at say 3 pm tells us what the temperature is, whether it is sunny, cloudy, raining or snowing, what the wind speed is and what is the direction of air flow etc. The weather in London after a little while may be vastly different - weather can change rapidly. Likewise, weather in Manchester at 3 pm might be completely different from that in London at that time.
Climate pertains to an average of atmospheric properties over a 30 year period and refers to an extended region. The region may be a county or a country or even larger areas.
Atmospheric gases are always moving causing weather to change continuously. Their mixing over an extended period of time enables us to describe an average atmospheric condition for the region. The set of such mean atmospheric conditions (temperature, rainfall, snowfall etc.) is the climate for that region.
Weather is the atmosphere that you feel while climate is what you expect the atmospheric conditions to be like - and the two can be very different. For example, for UK climate, I expect that the average temperature in July will be about 17C. In London the temperature in July may routinely change over a range from 10C to over 30C. Even within the UK, we can have several different climatic zones - Scottish climate is colder and wetter than the English climate.
Following slides demonstrate the difference between weather and climate
SLIDE 1: Data from
The data in slide 1 demonstrates the variability inherent in the weather at a location. Red and blue bars represent larger variations from the more normal weather (green bars) that one encounters. Even the green bars have significant range. The grey curve shows the observed maximum temperatures since records were kept. Interestingly, in many of the months in 2018, maximum monthly temperatures almost reached recorded maximum - an indication of global warming trends (more of this in later blogs).
Similar variability is observed in other atmospheric parameters like precipitation, wind speed etc.
The main take away from the figure is that weather does change rapidly over a large range - and it is highly unpredictable.
Climate, on the other hand averages out short-term variations and gives us a very good idea about what atmospheric conditions to expect (on average) in the vicinity of a particular location.
Slide 2 shows monthly averaged temperatures in the UK over 5 years. For a given month, there is still a spread but is typically less than 3C. Looking at slide 2, we could say that February in 2018 was 2C colder than January (but 3C warmer in 2019) - against an expectation of similar temperatures in both months.
SLIDE 2:
Climate of a region is defined as average atmospheric condition over 30 years. Atmospheric data are obtained from a large number of weather stations distributed in the region and a mean value calculated for each parameter.
One can then start to talk about annual mean temperatures (AMT) for a region or annual mean rainfall etc. Staying with the UK, Slide 3 shows how AMT has varied from 1910 to 2017. The fluctuations in AMT are typically half a degree centigrade from one year to the next.
SLIDE 3:
We make some interesting observations from this figure. Between 1961 and 2010, the 30-year mean temperature has increased by 0.4 to 0.5C for the UK and England. We can state that the UK climate has warmed by half a degree during the second half of the 20th century. The warming trend is particularly pronounced since 1990, although one can have (as in 2010 and 2011) a sharp drop in AMT for a brief period. From the data in the slide, I also notice that the English climate is 2C warmer than the Scottish climate.
I have discussed the case of the UK climate to demonstrate the difference between weather and climate. The warming trend over the last century or more is not particular to the UK only but the Earth's climate is showing a consistent warming trend - generally called Global Warming (GW) or Climate Change (CC).
Of all the atmospheric parameters, the temperature is the most important and is universally used as a primary indicator of the climate. Most input of energy to the Earth is from the Sun and majority of this energy is absorbed by the land and seas in the low to mid latitude regions lying on either side of the equator. The resulting increase in temperature of the tropics warms the atmosphere causing circulation of atmospheric air that then distributes the energy to northern latitudes. This drives wind currents which also carry the evaporated water from the oceans to create rain and snow. Distribution of air currents and precipitation determines the climate in different parts of the globe. See my blog on Air Circulations etc.
I shall discuss the global situation in my next blog.
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Much has been written about Climate Change (CC). I have been involved in creating public understanding of this important subject for the past 15 years. My general impression is that while there is more awareness of the term CC, there is not a great deal of enthusiasm/understanding among the general population about what may be done to alleviate the effects of CC. I shall publish a series of blogs to explain the science of CC in a way that a layperson without a science background can appreciate the situation.
I start by introducing the subject in a very general way:
During a cold spell, one hears comments like -
'So, where is Global Warming now?',
'Climate Change is not really happening',
'OK, Earth might have warmed a little, but it is getting colder again' etc.
Most of the time, these are genuinely felt comments from people not directly involved in meteorological investigations, and represent normal (defensive) reaction to the much talked about dire/threatening consequences of climate change. Climate Change (CC) is variously described to bring misery to the lives of billions of people - by causing extreme weather events, sea level rise, forced migration, droughts, famines and much else. Some people even call CC as an existential threat to the human race. But, this is all going to happen by the end of this century - most bad thing will properly be felt in 50 or 100 years time when a good fraction of people alive today will no longer be around.
That is the difficulty; CC is a problem of the distant future - we are okay today. It is easy to think that CC is not something that we need to pay too much attention just now - it is a few scientists who are making predictions on impending doom that may or may not happen but we are being asked to make some serious sacrifices in terms of changing the way we live, to give up our extravagant lifestyles - not eat meat products, reduce road and air travel and much more - in fact abstain from almost everything we enjoy. We are even asked to buy used clothes to save the planet.
It is not surprising that politicians and authorities in power do not take CC seriously - they have to win elections, safeguard their power base - one can't do that by asking voters to make serious sacrifices for something that is in the future and might not even happen. They pay lip service to mitigating, even reversing, CC but do little in practical terms.
Against such prevailing background of climate change scepticism, one has to work much harder to convey the scientific case for climate change to the general public. Scientists are particularly poor in their communication with communities and lay people whose lives will be impacted so severely by CC and who can put real pressure on politicians and authorities to take action.
Also, CC is a global phenomenon and must be addressed by all nations of the world in an effective way. So far, consensus on a global level has been specially difficult to achieve because vested interests - mostly the fossil fuel industry - have sabotaged/confused the science and it is not possible to agree on some fundamental causes of CC. Committing huge sums of money is not easy when the target has been made so fuzzy.
I list some obvious question with short answers:
- Who is responsible for CC? - Mostly developed nations in OECD so far, but recently China too.
- What has caused CC? - Population increase and unbridled, wasteful consumption habits are the primary reasons.
- What should be done to stop further damage by CC? - Control population and reduce consumption
- How does one achieve this? - Developed countries point finger at developing countries for recent increase in emissions of green house gases (GHG) leading to CC. Developing countries blame the rich countries to have caused the problem over the past 200 years. It does seem unreasonable for rich countries to ask others to stay poor while not wanting to sacrifice their high consumption lifestyles.
- Will renewable energy (RE) solve CC? - Hardly. The main problem is that too many people are consuming and wasting too many resources. RE is a mere diversion - it is too little and too late.
- Who will pay for CC mitigation/reversal? - Difficult question to answer. Nations have been making commitments since 1997 Kyoto protocol but have rarely implemented these.
- Is it too late to solve the CC conundrum? - Probably. Most scientific opinion is beginning to converge on a mean global temperature rise of about 3 degree centigrade (C) provided nations start to take some serious action. On the current trajectory, a rise of 4C or even greater is likely.
- Should one just give up and hope for the best? - Not advisable. To continue as now (business as usual) will create many bad situations that will be irreversible - some of them will cause runaway uncontrolled changes whose consequences cannot be predicted at present. In this scenario, CC might indeed become an existential threat for the human race.
- Who will be affected most by CC? - Majority of people in the developing countries and the poor in rich countries.
I have indicated here that overpopulation and overconsumption are the driving forces of CC. Until about 1990, OECD countries overconsumed resources and set CC in motion. With the emergence of China and to some extent India, a much larger population has joined the binge - resulting CC trajectory is looking much worse. Ironically, developed countries continue to consume several times greater resources per capita than people in developing countries do. The trajectory of resource consumption and hence global warming is very worrying.
Superficially, it appears that the developed countries in Europe and USA have controlled their emissions - but this is misleading. Developed countries have moved on from manufacturing to service industry and buy thier manufactured goods in great quantities from Asia - mainly China. While the emissions from China appear to be rising, a lot of these products are consumed in Europe and America.
Please click on the link below to understand the pressures that humans have put the Earth under, and how it is damaging our planet and destroying the welfare of future generations.
In the next blog, I shall explain the difference between weather and climate.
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'the pollution levels entered the "severe plus" or "emergency" category late Thursday night. Delhi Chief Minister ... described the city as a "gas chamber" while distributing 5 million breathing masks' .......... NDTV (1/Nov/2019) & BBC
Exactly a year ago, I had published an article detailing the science of outdoor air-pollution. It is responsible for more than 4 million premature deaths, largely from vehicles and industry, throughout the world. People in developing countries suffer the most serious pollution levels; people living in less affluent areas are the worst affected. Air pollution (indoors and outdoors) deaths in India are estimated at 2.5 million per year.
About 75% of outdoor air pollution is due to human activities. Most sources of air pollution are well beyond the control of individuals and demand/require concerted action by local and national level policy-makers working in sectors like transport, energy, waste management, urbal planning, and agriculture.
Historically, big cities in China and India have had the worst outdoor air pollution. China has taken steps to control pollution, reducing it by 17% between 2010 and 2015 but the situation in India has not improved at all. It is same story year after year. The slide shows the PM2.5 levels on 7th November 2017 in Delhi:
The outdoor air pollution is a problem not only in Delhi but in most of India. According to WHO, india has 14 out of the 15 top most polluted cities in the world in terms of PM2.5 concentrations. These are:
Delhi (153), Patna (149), Gwaliar (144), Raipur (134), Ahemdabad (100), Lucknow (96), Firozabad (96), Kanpur (93), Amritsar (92), Ludhiana (91), Allahabad (88), Agra (88) and Khanna (88)
In the end, the problem really boils down to the number of people living on the Earth. As more and more people move to western lifestyles with unbridled consumption; the human footprint, that is already too big, will increase further and our planet will just not be able to cope with the demands put on it.
Air pollution is just one of the ways that the Earth is responding to our irresponsibility.
PS: 4th November 2019: The Delhi pollution continues with authorities unable to provide a solution.
https://ektalks.blogspot.com/2018/11/air-pollution-invisible-killer.html
