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The question arose when I heard from friends across many countries that March has never been so hot. I myself felt the same in my city (Bangalore, India). Then I tried searching on internet, and I found a link on NASA, which says March 2016 was indeed hot.

I was wondering if experts can explain this rise in temperature? Is it due to higher $\ce{CO_2}$ levels due to human activity, or is it natural? Is it the start of unnatural global warming?

Matt Hall
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Gaurav Singhal
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    Higher CO2 levels. It's not the start of unnatural global warming - the warming is already underway. – Gimelist Apr 26 '16 at 12:53
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    You can usually find Monthly global temperature maps with a little googling. Here's March, 2016: http://www.ncdc.noaa.gov/sotc/service/global/map-blended-mntp/201603.gif and, already answered, but the primary drivers to warmer temperatures last month are man made climate change and the current El Nino. Locally there will always be some variation. – userLTK Apr 27 '16 at 11:07
  • Thank you guys, your comments are helpful. @userLTK, the graph that you have provided is really a very good picture of rising temperature. Thanks – Gaurav Singhal Apr 28 '16 at 08:42

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What happens in one city in one month is only a very very small part of the picture. You can make very little inference on global warming based on the weather in one city in one month.

You can make a little more inference on global warming based on the weather around the world in one month.

And we can say a lot about global warming based on the world's weather over a 30-year period.

A lot of heat got released from the ocean last year in the El Niño event: heat that had been accumulating in the oceans for a few years. That heat is now getting distributed around the world, which is why we're seeing rises in global surface temperatures - a similar thing happened back in 1997/8. The Earth has been accumulating a lot of heat for years, and it's now showing up as rises in surface temperatures.

The accumulation of heat is happening because the Earth has been absorbing more energy than it has been radiating away into space. That has happened because of human emissions of greenhouse gases, in particular, but not exclusively, carbon dioxide and methane.

Unnatural global warming started decades ago. Now, it's accelerating.

410 gone
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  • still need to ask my history of global warming question that asks exactly whether any scientists in the 19th century (during the Industrial Revolution) could have foreseen global warming two hundred years later. Probably not wouldn't you say? –  Apr 26 '16 at 15:06
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    @gansub - In 1896 (the tail end of the 19th century), Svante Arrhenius was the first to be concerned that burning fossil fuels and thereby adding carbon dioxide to the atmosphere could increase temperatures around the world. – David Hammen Apr 26 '16 at 15:22
  • Back on topic, the year after a strong El Nino is typically a very hot one. India is one of the many recipients of that extra heat. – David Hammen Apr 26 '16 at 15:23
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    @gansub they could have foreseen global warming, if they could have foreseen the scale of human consumption of fossil fuels. Arrhenius did the maths, but never imagined the accelerating rate at which fossil fuels would be consumed, so the timescales he foresaw were centuries out. And we've learnt a lot about forcings and feedbacks in the last century. – 410 gone Apr 26 '16 at 15:26
  • @DavidHammen - causes of past droughts e.g. in the 17th/18th century or earlier due to El Nino ? –  Apr 26 '16 at 16:05
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    @gansub -- If an answer is unclear and you desire clarification, ask away. On the other hand, it's better not to ask off-topic questions as a comment. Comments can be, and often are, deleted. Ask those separate questions as new questions. – David Hammen Apr 27 '16 at 23:37
  • Thanks @EnergyNumbers, your answer is very helpful. However, being a naive, I have got too many questions: What is meant by "a lot of heat got released", How much heat is a lot of heat to raise global temperature. Also, I thought Earth radiates all the energy it gets from Sun. Also if this a mix effect of El Niño and Global warming, then next year should global temperature go down a bit in next year, given the fact that since earth's atmosphere is warmer, it will radiate more heat this year. I need to read a lot, you don't need to answer everything, but if you have time, It will be helpful. – Gaurav Singhal Apr 28 '16 at 08:50
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    @GauravSinghal Because of humankind's greenhouse gas emissions, the earth now absorbs more heat than it radiates, and that's what's driving the warming of the oceans, the strong El Niño, global warming, and the catastrophic climate change that we're starting to see. After the 1997/8 El Niño, the upward trend in surface temperatures became less apparent in the annual global data, and we might indeed see the same again for a few years from 2017. – 410 gone Apr 28 '16 at 09:01
  • So one of the reason behind stronger El Niño is human activity. Thanks – Gaurav Singhal Apr 28 '16 at 09:12