| Date | November 2009 | Marks available | 2 | Reference code | 09N.3.sl.TZ0.E1 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe | Question number | E1 | Adapted from | N/A |
Question
It is now widely accepted that the increased production of carbon dioxide is leading to global warming.
Describe how carbon dioxide acts as a greenhouse gas.
Discuss the influence of increasing amounts of greenhouse gases on the environment.
Markscheme
long wavelength / infrared/IR radiation from Earth’s surface (some of this radiation) is absorbed (by gas);
Do not accept “trapped” or blocked.
Do not award mark for “IR from sun”.
causes (increased) vibration in bonds;
re-radiates heat back to the Earth;
Accept “re-transmits”
Do not accept “reflects/bounces”.
melting of polar ice caps/glaciers melting;
thermal expansion of oceans / rise in sea levels / coastal flooding;
stated effect on agriculture (e.g. crop yields changed);
changes in flora/plant/fauna/animal/insect distribution/biodiveristy;
Accept specific example.
stated effect on climate (e.g. drought / increased rainfall / desertification);
Do not accept “climate change” alone.
Do not allow “increased temperature/global warming” (given in question).
Award [1] each for any three.
Examiners report
As in previous sessions, most answers revealed that candidates are much better at describing the effects of greenhouse gases than explaining their interaction with different forms of radiation. Many candidates lost marks in (a) due to imprecise responses.
The earth “reflects” and CO2 "traps" were, as in previous sessions, all too common responses.
