Rising Surface Ozone Reduces Plant Growth And Adds To Global Warming

Increasing ozone near the Earth's surface could lead to significant reductions in regional plant production and crop yields.

Scientists from three leading UK research institutes have just released new findings that could have major implications for food production and global warming in the 21st century.

Experts from the Met Office, the University of Exeter and the Centre for Ecology & Hydrology, have found that projections of increasing ozone near the Earth's surface could lead to significant reductions in regional plant production and crop yields. Surface ozone also damages plants, affecting their ability to soak up carbon dioxide from the atmosphere and accelerating global warming.
Near-surface ozone has doubled since 1850 due to chemical emissions from vehicles, industrial processes, and the burning of forests. Dr Stephen Sitch, a climate impacts scientist at the Met Office Hadley Centre and lead author of the article, said: "Climate models have largely ignored atmospheric chemistry but in this research we have identified a cause of potentially increased warming with elevated levels of surface ozone likely to suppress plant growth."
Plants and soil are currently slowing--down global warming by storing about a quarter of human carbon dioxide emissions, but the new study suggests that this could be undermined by further increases in near-surface ozone. As a result more carbon dioxide would accumulate in the atmosphere and add to global warming. Co-author, Professor Peter Cox of the University of Exeter, explains: "We estimate that ozone effects on plants could double the importance of ozone increases in the lower atmosphere as a driver of climate change, so policies to limit increases in near-surface ozone must be seen as an even higher priority."
The research is published online in Nature July 25, 2007

GLOBAL WARMING

Global warming is 'irreversible'



The scientists concluded global temperatures could remain high for 1,000 years, even if carbon emissions can somehow be halted.
Their report was sponsored by the US Department of Energy and comes as President Obama announces a review of vehicle emission standards.
It appears in the journal Proceedings of the National Academy of Sciences.
The scientists have been researching global warming and the consequences for policymakers. The team warned that, if carbon levels in the atmosphere continued to rise, there would be less rainfall in already dry areas of southern Europe, North America, parts of Africa and Australia.
The scientists say the oceans are currently slowing down global warming by absorbing heat, but they will eventually release that heat back into the air.
They say politicians must now offset environmental damage already done by man-made pollution.
"People have imagined that if we stopped emitting carbon dioxide the climate would go back to normal in 100 years, 200 year - that's not true," said researcher Susan Solomon, the lead author of the report, quoted by AP news agency.
Their conclusions come as President Obama ordered the US Environmental Protection Agency to review rules on carbon emissions from passenger vehicles

Higher River Levels Predicted As More Carbon Dioxide Makes Plants Less Thirsty

Higher River Levels Predicted As More Carbon Dioxide Makes Plants Less Thirsty

Rising carbon dioxide levels will increase river levels in the future, according to a team of scientists from the Met Office Hadley Centre, the University of Exeter and the Centre for Ecology & Hydrology.

The findings, published on 30 August 2007 in the journal Nature, suggest that increasing carbon dioxide will cause plants to extract less water from the soil, leaving more water to drain into rivers which will add to the river flow increases already expected due to climate change.
Last year, members of the research team showed that this effect can already be seen in historical river flow records.
This new study shows that the effect of plant responses to carbon dioxide could be as important as those of increased rainfall due to man-made climate change.

CBSE SCIENCE MODEL QUESTION 10th STD

CBSE - SCIENCE

X – SECTION – A

PHYSICS AND CHEMISTRY


1. What is meant by the statement, “ potential difference between points A and B in an electric field is 1 volt.

2. Refractive index of media A, B, C and D are

i. A 1.33
ii. B 1.52
iii C 1.44
iv D 1.65
In which of the four media is the speed of light (i) maximum (ii) minimum.

3.What sign convention has been given to the focal length of a convex mirror

4.During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.

5.What is the colour of phenolphthalein indicator in an acidic solution.

6.Why does magnesium powder react much more rapidly than magnesium ribbon with dil.H2SO4

7.A student performs an experiment to study the magnetic effect of current around a current carrying straight conductor. He reports that the direction of deflection of the north pole of a compass needle kept at a given point near the conductor remains unaffected even when the terminals of the battery sending current in the wire are inter changed.for a given battery, the degree of deflection of a N-pole decreases when the compass is kept at a point farther away from the conductor.Which of the above observations of the student is incorrect and why?

8. What is the meaning of the term ‘frequency’ of an alternating current?What is value in India?
Why is an alternating current considered to be advantageous over direct current for long
range transmission of electric energy?

9. What are the two major shortcomings of Mendeleev’s periodic table? How have
these been removed in the modern periodic table?

10.Give reasons for the following.
i) Metals are regarded as electropositive elements.
ii) Articles made of Aluminium donot corrode even though Al is an active metal.

11.Draw the electron dot structures of ethane, ethene, and ethyne molecule.

12. Give reasons for the following.
Why do unsaturated hydrocarbons show addition reactions.
Why is the conversion of ethanol to ethanoic acid an oxidation reaction.
Alcohol supplied for industrial purposes is mixed with CuSO4

13. i. State Ohm’s law.
ii. Draw a schematic diagram of the circuit for studying ohm’s law
A wire of length L and resistance R is stretched so that its length is doubled and area of cross section is halved. How will its
i. resistance change, ii. Resistivity change.

14. A 14 year student is not able to see clearly the questions written on the black board placed at a distance of 5m from him.
Name the defect of vision he is suffering from.
With the help of labeled ray diagrams show how this defect can be corrected.
Name the type of lens used to correct this defect



15. Explain the construction and working of a electric motor.

OR

Give reasons for the following
:
i)The sky appears to be blue during day time to a person on earth.
ii) The sky near the horizon appears to have a reddish heu at the time of sunset and sunrise
iii) The sky appears dark instead of blue to an astronaut.
iv) The stars appears to twinkle
(v) The planets do not twinkle.







16. You are given the following materials:
Iron nails
Copper sulphate solution
Barium chloride solution
Copper powder
Ferrous sulphate crystals
Quick Lime

Identify the type of chemical reaction taking place when.

(a) Barium chloride solution is mixed with copper sulphate solution and a white
precipitate is observed.
(b) On heating copper powder in air in a China dish, the surface of copper powder
turns black.
(c) On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a gas having odour of burning sulphur is experienced.
(d) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away.
(e) Quick lime reacts vigorously with water releasing a large amount of heat.

OR
Four metals A, B, C and D are, in turn, added to the following solutions one by one. The observations made are tabulatd below:


Answer the following questions based on above information.
(i) Which is the most active metal and why? (ii) What would be observed if B is added to a solution of copper (II) sulphate and why?
(iii) Arrange the metals A, B, C and D in order of increasing reactivity.
(iv) Container of which metal can be used to store both zinc sulphate solution and
silver nitrate solution.
(v) Which of the above solutions can be easily stored in a container made up of any of
these metals?