Did you know?

Do all the all anthropogenic/natural emissions cause global warming? This question kept coming to me after I read about the effects of a few aerosols, especially sulphur dioxide (sources are: fossil fuels burning, metal smeltering, volcanic eruptions) and carbon rich aerosols (brown clouds), on solar insolations. The focus is on SO2 in this blog.

As per an editorial essay by P.J Crutzen some atmospheric particles (SO2 and organic carbon) act as reflectors and scatter solar radiations and prevent it from reaching the earth’s surface. In some cases these particles act as a nuclei for cloud droplets (forming brown clouds), where the water droplets coalesce around the pollutants, these then affect “the micro physical and optical properties of clouds, affecting precipitation and cloud albedo” (e.g. Rosenfeld, 2000; Ramanathan et al., 2001; Ramaswamy et al., 2001). These cool the earth's surface by reducing the incoming sunlight. This has been observed in volcanic eruptions e.g., during the volcanic eruption in June 1991,Mount Pinatubo injected some 10 Tg S, initially as SO2, into the tropical stratosphere (Wilson et al., 1993; Bluth et al., 1992). In this case the particles cooled the earth’s surface on average by 0.5 ◦ C in the year following the eruption (Lacis and Mishchenko, 1995). Effects of these clouds have been found to extend thousands of kilometers from the source. Studies reveal that reflective particles are found in the Troposphere and the Stratosphere, and these have a residence time of a week and one to two years respectively.

But on the other hand these aerosols cause acid rain (SO2) and may affect the hydrological cycle which affects agriculture (brown cloud), and also causes ecological damage (eg yellowing of the Taj Mahal). The pollution particles also cause more than 500,000 global premature deaths per year (as per the World Health Organization, Nel 2005). Although there is a lot of research required in this field, some believe that the increase in concentrations of these aerosols will be a solution to curb global warming. But this leads to a catch 22 situation. What is your opinion on this?

Report: http://www.guardian.co.uk/environment/2012/may/11/global-dimming-pollution

Dilemma!!!

Through a whole lot surveys carried out in India last year on the awareness of Global Warming and its implications, Mr. Samir Nazareth’s study revealed that a majority of people are unaware of the terminology (there is an urgent need for national awareness campaigns) although they had, to some extent, been affected by the impacts of climate change and knew that humans are the root cause of this global phenomenon. One of the questions out of the many that arose was whether this lack of awareness was working as a gain for some. Apart from the lack of casual evidence put forth to the public arena was identified, there is a lack of understanding among the public to change their consumption patterns. The people want to be informed, involved and want the government to take immediate and aggressive actions.

This is a very interesting report that I came across on how there is a need to clear the smog around Climate Change…

To get a detailed idea on this follow the link: http://www.thehindu.com/todays-paper/tp-opinion/clear-the-smog-around-climate-change-information/article4011367.ece

What should the Government and other environmental organizations focus on: working on Climate Change with just a few experts in this arena or should the focus be diverted temporarily to creating mass awareness campaigns which will get together a lot of people various fields?

Stay tuned, there’s a lot more coming your way.

 Thanks for reading…

Why have just a few gases made it to the GHG list?

When one kilogramme of gas is evaluated against the same amount of carbon dioxide in a stipulated time, we can find a measure of the relative global warming contribution, technically known as Global Warming Potential (GWP).The time span is significant to maintain uniformity in the GWP, as each Greenhouse Gas (GHG) has a different life span in the atmosphere before it breaks down or is removed. Normally, for official reports, a time span of 100 years is usually used. If a gas absorbs radiations of a wavelength which is already being absorbed by the atmosphere, then the GWP is low, on the other hand, if it absorbs light at a wavelength that normally passes through the atmosphere (without being absorbed) then the GWP is high.

Gases	Formula	Lifespan	GWP
			20	100		500
Carbon dioxide	CO2	Variable	1	1	1
Methane	CH4	12±3	72	25	7.6
Nitrous oxide	N2O	114	289	298	153
Sulphur hexafluoride	SF6	3200	16300	22800	32600
Chlorofluorocarbons	CFC12	45	1100	10,900	5200

Since the industrial revolution, concentrations of greenhouse gases have increased linearly. The GHGs are found to have a tendency to absorb and emit infrared (thermal) radiations. These gas molecules have two or more component atoms, which are loosely bound, due to which they vibrate on absorption of heat. When the infrared radiations strike a molecule such as carbon dioxide and causes its bonds to bend and vibrate (this is called the absorption of IR energy), the molecule gains extra kinetic energy that may either be transmitted to other molecules through molecular collision or be re-radiated back to the space, earth causing a general heating of the earth and near surface atmosphere. The major components of the atmosphere (N2 and O2) are two-atom molecules are tightly bound, and so they cannot vibrate, as a consequence they neither absorb heat nor do they contribute to the greenhouse effect. On the contrary it is believed that these gases allow the radiations to pass through the (near surface) atmosphere.

                                 Eg of effect of infrared radiations on CO2 gas. 

The dips in the lines are caused by the absorption of energy; hence only 10% of the energy is transmitted.

Due to accelerated anthropogenic activities (combustion of fossil fuels, deforestation etc) and the long life span (variable), the concentrations of CO2 are relatively high amongst all the other gases making it the dominant GHG. Although water vapor is the real strongest GHG in the atmosphere its concentration is kept in control due to precipitation and so they are not as harmful as CO2.

I hope this blog helped in understanding why the GHG’s cause global warming.

Thank you for reading, stay tuned there is a lot more coming up. 

Rethink our actions!!!

One of the global concerns of most nations (both developed and developing) is “Global Warming”. Like a coin has two sides this topic has two approaches, one outlook states that this is a natural phenomena while most strongly believe that the anthropogenic activities have accelerated this process. I believe that the anthropogenic activities are not the solitary contributors of climate change; the natural phenomena’s (plate tectonics, volcanic eruptions, solar variations, and orbital variations, all of which occur over a long period of time) also contribute to a small percentage of climate variations (evident from the RF values).

To correlate global warming with anthropogenic activities one needs to understand the Earth’s energy system and the variations occurring in it. The incoming solar insolation/shortwave and outgoing infrared radiation/longwave should be (on an average) in equilibrium (first law of thermodynamics). These energy fluxes govern the temperature of the Earth’s surface and atmosphere.

  

  An “imbalance” in the energy budget of the Earth-atmosphere system is Radiative Forcing (RF, W/ m2), which is measured at the tropopause. RF is a simple method to quantitatively assess and compare the natural and anthropogenic causes of the climate change. The GHG’s absorb the infrared (thermal) radiations emitted by the earth into the space (causing a rise in temperature) and this forms the basis of RF measurements. Positive RF (mostly due to GHG’s with longer life spans, aerosols, albedo’s) indicates warming of the Earth’s surface and lower atmosphere, while negative RF has a reversal effect.

The table below illustrates the extent of RF caused by anthropogenic (green) and natural (red) agents (For a detailed representation of RF see: Table 2.12 in the following link: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf)

RF agents	RF (W/m²)
Carbon dioxide	+1.66
Methane	+0.48
Nitrous oxide	+0.16
Water vapour	+0.07
Total direct aerosols	-0.50 [±0.40]
Cloud albedo effect	-0.70
Surface albedo(landuse)	-0.20
Surface albedo BC aerosol on snow	+0.10[±0.10]
Solar irradiance	+0.12
Volcanic aerosols	Negligible

It is evident from the table that the net anthropogenic RF surpasses the RF of natural processes. Also the increase in the concentrations of greenhouse gases will reduce the efficiency of radiation from the Earth’s surface to the space. This enhances the greenhouse effect (an effect that has been operating in the Earth’s atmosphere for billions of years due to the presence of naturally occurring greenhouse gases and natural agents), thus causing global warming. 

 I feel that we have both history and science as guides, so why not make conscious efforts?

Thank you for reading. 

 

P.S: In my blogs I will be focusing on carbon dioxide (the chemistry behind why it is considered the most potent GHG, the sector based emissions with UK as a case study and then will talk about the different strategies that are and can be implemented to reduce sector specific emissions). I will also blog about a few interesting reports/news (current issues of climate change may not be linked with my blog topics, but when we talk about the environment we need a holistic approach and understanding of the various aspects) from India and UK and some interesting facts about other GHG's.