Today's Headlines - 02 August 2023
Climate change is altering the colour of the oceans
GS Paper - 3 (Environment)
The colour of the Earth’s oceans has significantly altered over the past two decades, most likely due to human-induced climate change, according to a new study. Over 56 per cent of the oceans, more than the total land area on the planet, has experienced the shift in colour, it added. The study, ‘Global climate-change trends detected in indicators of ocean ecology’, was published in the journal Nature.
What makes the oceans colourful in the first place?
In most regions across the world, the oceans appear blue or navy blue for a reason. This happens due to “the absorption and scattering of light”.
When the sunlight falls on deep and clear water, colours with longer wavelengths, such as red, yellow and green, are absorbed by the water molecules but blue and violet, which have a much shorter wavelength, are reflected back.
When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters.
The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
But when the water isn’t deep or clean, an ocean can appear to be of a different colour.
For instance, along Argentina’s coastline, where major rivers merge into the Atlantic Ocean, the ocean exudes a brown tint because of dead leaves and sediments spewing from the rivers.
In other parts of the world, the oceans appear green, which happens due to the existence of phytoplankton on the upper surface of the water.
Phytoplanktons are microscopic marine algae that contain the green-coloured pigment chlorophyll.
The pigment helps them absorb sunlight, which they use to capture carbon dioxide from the atmosphere and convert it into sugars. Moreover, chlorophyll absorbs the red and blue portions of the light spectrum — or photosynthesis — and reflects green light.
What methods were used to carry out the study?
To conduct the study, Cael and his team first analysed data from Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA’s Aqua satellite, which has been monitoring ocean colour since 2002 — the measurements are taken in terms of the amount of light coming off the surface of the oceans, at all seven of the different wavelengths of light, from violet to red.
The examination of 20 years worth of data indicated that in more than 50 per cent of the world’s oceans, the colour has changed.
Then, to check if the phenomenon has occurred due to climate change, researchers used a climate model – a computer representation of the Earth.
This model simulated the planet’s oceans under two scenarios: one with the addition of greenhouse gases, and the other without it.
The greenhouse-gas model predicted that a significant trend should show up within 20 years and that this trend should cause changes to ocean colour in about 50 percent of the world’s surface oceans — almost exactly what Cael found in his analysis of real-world satellite data.
#upsc #news #headline #climate #colour #oceans #pigment #phytoplankton #chlorophyll #sediments #spewing #rivers #spectrum #methods #MODIS #NASA #Aqua #satellite #world #earth #wavelength #gases #greenhouse #data #planet
Climate change is altering the colour of the oceans
GS Paper - 3 (Environment)
The colour of the Earth’s oceans has significantly altered over the past two decades, most likely due to human-induced climate change, according to a new study. Over 56 per cent of the oceans, more than the total land area on the planet, has experienced the shift in colour, it added. The study, ‘Global climate-change trends detected in indicators of ocean ecology’, was published in the journal Nature.
What makes the oceans colourful in the first place?
In most regions across the world, the oceans appear blue or navy blue for a reason. This happens due to “the absorption and scattering of light”.
When the sunlight falls on deep and clear water, colours with longer wavelengths, such as red, yellow and green, are absorbed by the water molecules but blue and violet, which have a much shorter wavelength, are reflected back.
When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters.
The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
But when the water isn’t deep or clean, an ocean can appear to be of a different colour.
For instance, along Argentina’s coastline, where major rivers merge into the Atlantic Ocean, the ocean exudes a brown tint because of dead leaves and sediments spewing from the rivers.
In other parts of the world, the oceans appear green, which happens due to the existence of phytoplankton on the upper surface of the water.
Phytoplanktons are microscopic marine algae that contain the green-coloured pigment chlorophyll.
The pigment helps them absorb sunlight, which they use to capture carbon dioxide from the atmosphere and convert it into sugars. Moreover, chlorophyll absorbs the red and blue portions of the light spectrum — or photosynthesis — and reflects green light.
What methods were used to carry out the study?
To conduct the study, Cael and his team first analysed data from Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA’s Aqua satellite, which has been monitoring ocean colour since 2002 — the measurements are taken in terms of the amount of light coming off the surface of the oceans, at all seven of the different wavelengths of light, from violet to red.
The examination of 20 years worth of data indicated that in more than 50 per cent of the world’s oceans, the colour has changed.
Then, to check if the phenomenon has occurred due to climate change, researchers used a climate model – a computer representation of the Earth.
This model simulated the planet’s oceans under two scenarios: one with the addition of greenhouse gases, and the other without it.
The greenhouse-gas model predicted that a significant trend should show up within 20 years and that this trend should cause changes to ocean colour in about 50 percent of the world’s surface oceans — almost exactly what Cael found in his analysis of real-world satellite data.
#upsc #news #headline #climate #colour #oceans #pigment #phytoplankton #chlorophyll #sediments #spewing #rivers #spectrum #methods #MODIS #NASA #Aqua #satellite #world #earth #wavelength #gases #greenhouse #data #planet
Today's Headlines - 01 September 2023
Super Blue Moon of Raksha Bandhan
GS Paper - 3 (Science and Technology)
The Raksha Bandhan full moon on 30-31 August was unusual: it was both a “blue moon” and a “super moon” and therefore, a “Super Blue Moon”, a rare trifecta of astronomical events.
What is a supermoon?
The orbit of the moon around the earth is not circular; it is elliptical, that is, an elongated or stretched-out circle. It takes the moon 27.3 days to orbit the earth.
It is 29.5 days from new moon to new moon, though. This is because while the moon is orbiting the earth, both the earth and the moon are also moving around the sun — and it takes additional time for the sun to light up the moon in the same way as it does at the beginning of every revolution around the earth.
The new moon is the opposite of the full moon — it is the darkest part of the moon’s invisible phase, when its illuminated side is facing away from the earth.
The point closest to earth in the moon’s elliptical orbit is called perigee, and the point that is farthest is called apogee.
A super moon happens when the moon is passing through or is close to its perigee, and is also a full moon. (This happens with a new moon as well, just that it is not visible.
A full moon occurs when the moon is directly opposite the sun (as seen from earth), and therefore, has its entire day side lit up. The full moon appears as a brilliant circle in the sky that rises around sunset and sets around sunrise. The moon appears ‘full’ not just on Purnima, but also on the night before and after the full moon night.
What is a blue moon?
Though the expression “once in a blue moon” implies a rare or unusual occurrence, a blue moon is not that rare an astronomical phenomenon.
There are a couple of definitions of a blue moon, but the one that is most commonly understood — and is endorsed by NASA — describes the situation when a full moon is seen twice in a single month.
Because the new moon to new moon cycle lasts 29.5 days, a time comes when the full moon occurs at the beginning of a month, and there are days left still for another full cycle to be completed.
Such a month, in which the full moon is seen on the 1st or 2nd, will have a second full moon on the 30th or 31st. According to NASA, this happens every two or three years.
The first full moon of August 2023 occurred on 1 August. That was also a super moon, but the super moon of 30-31 August will be bigger because the moon is now closer to the perigee.
Will the moon actually appear blue?
No. Sometimes, smoke or dust in the air can scatter red wavelengths of light, as a result of which the moon may, in certain places, appear more blue than usual. But this has nothing to do with the name “blue” moon.
Speaking of colours, you may have noticed that the moon appears more yellow/ orange when it is lower in the sky (closer to the horizon).
This is because moonlight travels for longer through the atmosphere at this stage, and along the way, more of the shorter, bluer wavelengths of light are scattered, leaving more of the longer, redder wavelengths.
NASA points out that dust or pollution can end up deepening the reddish colour of the moon.
#upsc #news #headline #superbluemoon #rakshabandhan #science #technology #fullmoon #supermoon #trifecta #astronomicalevents #orbit #earth #newmoon #ellipticalorbit #apogee #purnima #phenomenon #air #wavelength #yellow #orange #atmosphere #NASA #dust #pollution #reddishcolour
Super Blue Moon of Raksha Bandhan
GS Paper - 3 (Science and Technology)
The Raksha Bandhan full moon on 30-31 August was unusual: it was both a “blue moon” and a “super moon” and therefore, a “Super Blue Moon”, a rare trifecta of astronomical events.
What is a supermoon?
The orbit of the moon around the earth is not circular; it is elliptical, that is, an elongated or stretched-out circle. It takes the moon 27.3 days to orbit the earth.
It is 29.5 days from new moon to new moon, though. This is because while the moon is orbiting the earth, both the earth and the moon are also moving around the sun — and it takes additional time for the sun to light up the moon in the same way as it does at the beginning of every revolution around the earth.
The new moon is the opposite of the full moon — it is the darkest part of the moon’s invisible phase, when its illuminated side is facing away from the earth.
The point closest to earth in the moon’s elliptical orbit is called perigee, and the point that is farthest is called apogee.
A super moon happens when the moon is passing through or is close to its perigee, and is also a full moon. (This happens with a new moon as well, just that it is not visible.
A full moon occurs when the moon is directly opposite the sun (as seen from earth), and therefore, has its entire day side lit up. The full moon appears as a brilliant circle in the sky that rises around sunset and sets around sunrise. The moon appears ‘full’ not just on Purnima, but also on the night before and after the full moon night.
What is a blue moon?
Though the expression “once in a blue moon” implies a rare or unusual occurrence, a blue moon is not that rare an astronomical phenomenon.
There are a couple of definitions of a blue moon, but the one that is most commonly understood — and is endorsed by NASA — describes the situation when a full moon is seen twice in a single month.
Because the new moon to new moon cycle lasts 29.5 days, a time comes when the full moon occurs at the beginning of a month, and there are days left still for another full cycle to be completed.
Such a month, in which the full moon is seen on the 1st or 2nd, will have a second full moon on the 30th or 31st. According to NASA, this happens every two or three years.
The first full moon of August 2023 occurred on 1 August. That was also a super moon, but the super moon of 30-31 August will be bigger because the moon is now closer to the perigee.
Will the moon actually appear blue?
No. Sometimes, smoke or dust in the air can scatter red wavelengths of light, as a result of which the moon may, in certain places, appear more blue than usual. But this has nothing to do with the name “blue” moon.
Speaking of colours, you may have noticed that the moon appears more yellow/ orange when it is lower in the sky (closer to the horizon).
This is because moonlight travels for longer through the atmosphere at this stage, and along the way, more of the shorter, bluer wavelengths of light are scattered, leaving more of the longer, redder wavelengths.
NASA points out that dust or pollution can end up deepening the reddish colour of the moon.
#upsc #news #headline #superbluemoon #rakshabandhan #science #technology #fullmoon #supermoon #trifecta #astronomicalevents #orbit #earth #newmoon #ellipticalorbit #apogee #purnima #phenomenon #air #wavelength #yellow #orange #atmosphere #NASA #dust #pollution #reddishcolour