UGC NET Climate Models, Scenarios & Downscaling: practice questions

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 papers

10worked here, free

17written to this exam in this subject

8syllabus units

What this subject covers

How future climate is projected and how to use projections responsibly: model hierarchy, CMIP ensembles, RCP and SSP scenarios, downscaling and bias correction, and uncertainty. Needed for impact studies, climate-risk disclosure and adaptation planning.

In the exams: GARP SCR 'Climate Models and Scenario Analysis'; PG and PhD research in agrometeorology and climate change; ICAR AICE subject 60 (climate variability)

Model hierarchy: energy-balance, GCM, ESM and regional models
CMIP ensembles and model evaluation
Representative Concentration Pathways and Shared Socioeconomic Pathways
Integrated assessment models and mitigation pathways
Statistical and dynamical downscaling
Bias correction methods
Sources of uncertainty: scenario, model and internal variability
Seasonal and sub-seasonal forecasting
Climate indices and extreme-event indices
Using climate data portals and open datasets
Scenario analysis for organisations: physical and transition scenarios

What UGC NET asks from it

CSIR-UGC NET — Earth, Atmospheric, Ocean and Planetary Sciences

Energy-balance models and response time, GCM structure and parameterisation, predictability and chaos, ENSO and MJO, forecast verification and scenario frameworks.

UGC NET Environmental Sciences (Unit 9 and Unit 10)

Modelling concepts, IPCC scenarios and projections, statistical approaches including downscaling, and contemporary climate issues.

Where the 17 questions fall

How our questions for UGC NET spread across the units of Climate Models, Scenarios & Downscaling. Difficulty: 10 easy, 7 medium, 0 hard.

Representative Concentration Pathways and Shared Socioeconomic Pathways	5
Model hierarchy: energy-balance, GCM, ESM and regional models	3
CMIP ensembles and model evaluation	2
Statistical and dynamical downscaling	2
Sources of uncertainty: scenario, model and internal variability	2
Integrated assessment models and mitigation pathways	1
Climate indices and extreme-event indices	1
Scenario analysis for organisations: physical and transition scenarios	1

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Model hierarchy: energy-balance, GCM, ESM and regional models · medium

Why are two-layer energy-balance models used as emulators in IPCC assessments and integrated assessment models?

They resolve regional rainfall in more detail than any general circulation model can
They include every biogeochemical cycle and so replace Earth system models entirely
They mimic the fast and slow responses of complex models at negligible cost
They are the only models that can be run with emissions rather than concentrations

Answer and working

C. They mimic the fast and slow responses of complex models at negligible cost

A mixed-layer plus deep-ocean box captures the fast and slow modes of global temperature response and can be calibrated to complex models, so it can emulate them cheaply. Such models have no regional rainfall detail, omit most biogeochemistry, and are not unique in being emissions-driven.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

2 · CMIP ensembles and model evaluation · easy

Which CMIP phase provided the main model simulations for the IPCC Sixth Assessment Report?

CMIP6
CMIP5
CMIP3
CMIP7

Answer and working

A. CMIP6

CMIP6 underpinned AR6; CMIP5 underpinned AR5 and CMIP3 underpinned AR4. CMIP7 is under way for later assessments.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

3 · CMIP ensembles and model evaluation · medium

Under which organisation is the Coupled Model Intercomparison Project coordinated?

UNFCCC Subsidiary Body for Implementation
International Energy Agency's modelling division
World Bank's climate finance unit
WCRP's Working Group on Coupled Modelling

Answer and working

D. WCRP's Working Group on Coupled Modelling

CMIP is organised by WCRP's Working Group on Coupled Modelling. The UNFCCC, IEA and World Bank use CMIP results but do not run it.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

4 · Representative Concentration Pathways and Shared Socioeconomic Pathways · easy

What does the number 4.5 in the scenario name RCP4.5 refer to?

Atmospheric CO₂ concentration in hundreds of ppm in 2100
Global warming in °C by 2100 relative to 1850–1900
Approximate radiative forcing in W m⁻² around 2100
Annual emissions in gigatonnes of carbon in 2050

Answer and working

C. Approximate radiative forcing in W m⁻² around 2100

RCP numbers give the approximate radiative forcing in W m⁻² reached around 2100. They are not temperatures, concentrations or emission rates.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

5 · Representative Concentration Pathways and Shared Socioeconomic Pathways · easy

What is AR6's best estimate of global warming in 2081–2100, relative to 1850–1900, under SSP2-4.5?

2.7 °C
1.8 °C
3.6 °C
4.4 °C

Answer and working

A. 2.7 °C

AR6 best estimates: SSP1-1.9 1.4 °C, SSP1-2.6 1.8 °C, SSP2-4.5 2.7 °C, SSP3-7.0 3.6 °C, SSP5-8.5 4.4 °C.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

6 · Representative Concentration Pathways and Shared Socioeconomic Pathways · medium

How did the RCP process differ from the earlier SRES approach?

RCPs included only policy scenarios, while SRES included only scenarios with strong mitigation
Concentration pathways came first, so climate and social modelling ran in parallel
Socioeconomic storylines were written first, and emissions were then derived from them in sequence
RCPs were developed by a single modelling centre, while SRES used dozens of centres

Answer and working

B. Concentration pathways came first, so climate and social modelling ran in parallel

The RCP approach defined forcing pathways first, letting climate modellers start while SSP narratives were developed in parallel. SRES derived emissions from storylines in sequence and had no explicit climate policy.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

7 · Representative Concentration Pathways and Shared Socioeconomic Pathways · easy

Which scenario family underpinned the IPCC Third and Fourth Assessment Reports?

Representative Concentration Pathways
Shared Socioeconomic Pathways
NGFS climate scenarios
SRES storylines such as A1, A2, B1 and B2

Answer and working

D. SRES storylines such as A1, A2, B1 and B2

SRES (2000) storylines were used in AR3 and AR4; RCPs were introduced for AR5; SSP-based scenarios were central to AR6; NGFS scenarios are for financial supervisors.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

8 · Integrated assessment models and mitigation pathways · medium

Roughly when is net zero CO₂ reached in AR6 pathways that limit warming to 2 °C with a greater than 67 per cent chance (C3)?

Early 2030s
Early 2050s
After 2150
Early 2070s

Answer and working

D. Early 2070s

C3 pathways reach net zero CO2 in the early 2070s; C1 pathways in the early 2050s.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

9 · Climate indices and extreme-event indices · medium

How is the Dipole Mode Index for the Indian Ocean Dipole defined?

Pressure difference between the Azores high and the Icelandic low
West minus south-east tropical Indian Ocean SST anomaly
Sea surface temperature anomaly in the Niño 3.4 region of the Pacific
Sea-level pressure at Tahiti minus sea-level pressure at Darwin

Answer and working

B. West minus south-east tropical Indian Ocean SST anomaly

The DMI is the SST anomaly difference between the western and south-eastern equatorial Indian Ocean. Tahiti–Darwin is the Southern Oscillation Index, Niño 3.4 is ENSO, and Azores–Iceland is the NAO.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

10 · Scenario analysis for organisations: physical and transition scenarios · easy

Climate scenarios used by organisations are best described as

the most likely future, chosen by averaging all models
worst-case outcomes only, used to set insurance premiums
official predictions of the future issued by central banks
plausible, internally consistent descriptions of possible futures, not forecasts

Answer and working

D. plausible, internally consistent descriptions of possible futures, not forecasts

Scenarios span plausible futures to test strategies; they are not predictions, averages or worst cases only.

Further reading: See the manual sources: IPCC AR6 WGI/WGIII, CMIP6 design papers, ETCCDI and the documents named in the explanation

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