UGC NET — Environmental Sciences (subject code 89) · India · National Testing Agency for the University Grants Commission
Original practice questions written to the published syllabus · not past papersThe physical basis of climate change as assessed by the IPCC: the greenhouse effect, radiative forcing, the global carbon cycle, feedbacks, climate sensitivity, and the evidence for observed change. It goes well beyond the 'climate change and livestock' unit of veterinary environmental hygiene.
In the exams: GATE ES Section 8 (greenhouse gases, global warming); UGC NET Environmental Sciences Unit 10; GARP SCR 'Foundations of Climate Change'; UPSC CSE environment
UGC NET Environmental Sciences (Unit 10) and CUET-PG Environmental Sciences
Recall of IPCC structure and findings, GWP values by assessment report, residence times, ocean acidification chemistry, sea level contributions, Milankovitch cycles and the components of the climate system, usually as assertion–reason and matching items.
CSIR-UGC NET Earth, Atmospheric, Ocean and Planetary Sciences
Radiative transfer and the energy budget, emission height and lapse rate, feedback analysis and sensitivity, carbonate chemistry and the Revelle factor, ENSO and modes of variability, palaeoclimate and orbital forcing.
How our questions for UGC NET spread across the units of Climate System Science. Difficulty: 13 easy, 17 medium, 3 hard.
| IPCC assessment process and confidence language | 6 | |
| Observed changes: temperature, precipitation, sea level, cryosphere | 4 | |
| The climate system and its components | 3 | |
| Radiative forcing and global warming potential (GWP, GTP, GWP*) | 3 | |
| The global carbon cycle: pools, fluxes and the airborne fraction | 3 | |
| Methane and nitrous oxide budgets | 3 | |
| Ocean warming, deoxygenation and acidification | 3 | |
| Aerosols and their climate effects | 2 | |
| Tipping points and irreversibility | 2 | |
| The natural greenhouse effect and the energy budget | 1 | |
| Climate feedbacks and equilibrium climate sensitivity | 1 | |
| Detection and attribution, including extreme-event attribution | 1 | |
| Carbon budgets and the link between cumulative emissions and warming | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Antarctic ice cores covering the last 800,000 years show atmospheric carbon dioxide varying with the glacial cycles. Which range matches the record before industrialisation?
C. Between near 180 ppm in glacials and near 280 ppm in interglacials
Ice cores show CO2 swinging between about 180 and 280 ppm. Values near 410 ppm were reached only recently through human emissions, and CO2 was not constant: it acted as an amplifying feedback on orbital forcing alongside methane.
Further reading: IPCC AR6 WGI (2021) and the IPCC 2006 Guidelines / 2019 Refinement where cited
How does effective radiative forcing (ERF), the measure used throughout AR6, differ from stratospherically adjusted radiative forcing?
C. ERF also lets fast tropospheric, cloud and land adjustments occur while surface temperature is held fixed
Adjusted RF lets only the stratosphere re-equilibrate. ERF also allows rapid adjustments in tropospheric temperature, water vapour, clouds and land surface with global surface temperature fixed, and so predicts temperature response more consistently across agents. The instantaneous measure allows no adjustment, and an equilibrium state would be a response, not a forcing.
Further reading: IPCC AR6 WGI (2021) and the IPCC 2006 Guidelines / 2019 Refinement where cited
Which reservoir is the largest pool of carbon that exchanges with the atmosphere on time scales of up to a few thousand years?
A. The ocean, mostly as dissolved inorganic carbon
The ocean holds about 38,000 PgC, overwhelmingly as dissolved inorganic carbon, far more than the atmosphere (~870 PgC), vegetation (~450–650 PgC) or soils (~1500–2400 PgC).
Further reading: IPCC AR6 WGI (2021) and the IPCC 2006 Guidelines / 2019 Refinement where cited
Which evidence shows that the rise in atmospheric CO₂ since industrialisation comes mainly from fossil carbon?
D. A falling ¹³C/¹²C ratio in atmospheric CO₂ together with falling atmospheric oxygen
Fossil carbon is depleted in ¹³C and free of ¹⁴C, so its addition lowers ¹³C/¹²C (the Suess effect), and combustion consumes oxygen. Ocean pH is falling, not rising, and CO2 is higher in the Northern Hemisphere where most emissions occur.
Further reading: IPCC AR6 WGI (2021) and the IPCC 2006 Guidelines / 2019 Refinement where cited
AR6 assessed global surface temperature in 2011–2020 relative to 1850–1900. Which value is correct?
C. 1.09 °C warmer
AR6: 1.09 °C (very likely 0.95–1.20 °C). 1.59 °C is the land-only warming; 2.72 is the total anthropogenic ERF in W m⁻², not a temperature; 0.45 is TCRE per 1000 GtCO2.
Further reading: IPCC AR6 WGI (2021) and the IPCC 2006 Guidelines / 2019 Refinement where cited
Which publication sequence matches the IPCC Sixth Assessment cycle?
D. WGI 2021; WGII and WGIII 2022; Synthesis Report 2023
AR6: WGI August 2021, WGII February 2022, WGIII April 2022, Synthesis Report March 2023. 2014 belongs to AR5; 2018–2019 was the period of the AR6 special reports.
Further reading: IPCC AR6 WGI (2021) and the IPCC 2006 Guidelines / 2019 Refinement where cited
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