The scientific view is that the increase in global temperature should not exceed 2 ℃ above pre-industrial level. If the global temperature increases beyond 3 ℃ above the pre-industrial level, what can be its possible impact/impacts on the world? 1. Terrestrial biosphere tends toward a net carbon source. 2. Widespread coral mortality will occur. 3. All the global wetlands will permanently disappear. 4. Cultivation of cereals will not be possible anywhere in the world. Select the correct answer using the code given below.

States that higher temperatures and reduced rainfall can decrease soil moisture, suppress plant growth and agricultural yields — a rule linking warming to reduced terrestrial productivity.

A student could combine this with the basic idea that lower plant growth reduces ecosystem carbon uptake to infer that strong warming might weaken the land carbon sink and possibly turn it into a source.

Describes ‘catastrophic global warming’ impacts on agriculture and notes rising greenhouse gas concentrations (e.g., methane) — indicating stronger feedbacks and ecosystem stress under large warming.

Using this pattern, a student could argue that more severe warming (≫2°C) increases ecosystem damage and greenhouse gas releases, which could shift net land carbon balance toward a source.

Gives the concept of temperature thresholds (e.g., staying below specified °C increases to avoid worst effects), implying impacts escalate with larger temperature increases.

A student could extend this threshold idea to reason that exceeding higher thresholds (such as 3°C) likely produces much larger biosphere impacts that could undermine terrestrial carbon uptake.

Explains that increased CO2 and warming arise from fossil-fuel burning and that CO2 strongly affects the heat budget — linking human emissions to rising temperatures that stress ecosystems.

Combined with maps or emissions scenarios, a student could infer that continued emissions driving >3°C warming would amplify stressors on land biota, making a net source outcome more plausible.

States coral species live within a relatively narrow temperature margin and that anomalously high sea temperatures can induce coral bleaching.

A student could combine this with basic facts about how a >3°C global mean rise likely raises sea-surface temperatures in the tropics to judge increased bleaching risk and potential mortality.

Notes bleaching epidemics can cause mass (catastrophic) mortality of corals and links reefs' vulnerability to elevated stressors.

One could map regions of known reef distribution against projected SST increases under >3°C warming to assess probable scale of mortality.

Gives a temperature range in which corals thrive (18–30°C) and states bleaching is more frequently reported from elevated sea-water temperatures.

Using current tropical SSTs and a >3°C increase, a student can estimate where local temperatures would exceed corals' tolerable range and infer likely bleaching hotspots.

Identifies ocean warming and ocean acidification as climate-change impacts expected to negatively affect corals and their ecosystems.

A student can combine projected CO2-driven acidification and >3°C warming scenarios with coral sensitivity to both stressors to assess cumulative mortality risk.

Explicitly states corals are dying at an unprecedented rate and attributes coral bleaching to rise in ocean temperatures.

A student could take this attribution plus knowledge of how extreme warming events scale with global mean temperature to infer larger-scale bleaching under >3°C warming.

States higher temperatures and less rainfall in some areas can decrease soil moisture and suppress plant growth, and species (plants/animals) shift poleward and to higher elevations.

A student could map where wetlands rely on local precipitation vs. inflows and infer that some inland wetlands may dry while others could persist or shift poleward/elevationally.

Predicts melting polar ice and glaciers and a resulting rise in sea level as a consequence of warming.

Combine sea-level rise projections with locations of coastal wetlands (mangroves, saltmarshes) on a world map to assess which coastal wetlands are at risk of inundation or migration limits.

Lists observed changes from warming: sea level rise, ocean warming, permafrost melt, vegetation moving upward, and poleward spread of diseases—demonstrating multiple ecosystem impacts.

Use these multiple pressure types to reason that different wetland types (coastal, peatland/permafrost, alpine, tropical freshwater) will face different threats and thus not all would respond identically.

Links catastrophic warming to melting ice-caps, sea-level rise, storminess, droughts and floods—factors that alter wetland extent and hydrology.

A student could assess how combined increased storm surge plus sea-level rise threatens some coastal wetlands while increased drought frequency threatens seasonal freshwater wetlands inland.

Gives regional projections of 3–5°C warming in parts of India and notes increased cyclone frequency/intensity—illustrating heterogeneous regional impacts at ~3°C warming.

Extrapolate that since warming is regionally variable, some wetlands will experience more severe local change (and possible loss) while others may be less affected or change in different ways.