Satellite records show that a lake’s seasonal surface ice now breaks up earlier than it did several decades ago. The shift matches a climate model’s prediction that warming would advance breakup, and the measured rise in air temperature near the lake is close to the rise used in the model. In the initial simulation, however, river flow and wind were held constant. ______ the model’s authors note that when the simulation is rerun with the observed changes in river flow and wind, it produces breakup dates nearly as early as those in the satellite record even if the temperature input is held at its earlier level.
Which choice completes the text with the most logical transition?
For difficult transition questions, identify both the broad relationship and its exact scope. When a sentence introduces an alternative way to produce the same result, determine whether it challenges the observation itself, the model’s predictive ability, or only the causal conclusion drawn from agreement between the model and the observation. Also verify that a sentence-opening modifier logically describes the subject that follows it.
Hints
Separate observation from explanation
Identify what the satellite record directly establishes and what the model is being used to explain.
Compare the simulations
Consider what it means that similar breakup dates result from two different sets of inputs.
Check the scope of each option
Ask whether the final sentence challenges a measurement, changes the model’s range, supports an assumption, or affects a causal interpretation.
Step-by-step Explanation
Identify the apparent support
The observed breakup shift matches the initial simulation, and the measured temperature rise is close to the rise used in that simulation. These correspondences initially make the warming-based explanation seem persuasive.
Examine the simulation conditions
The initial simulation held river flow and wind constant, although those factors changed at the actual lake. Therefore, the simulation’s controlled conditions do not fully match the real-world conditions.
Interpret the revised result
When the observed changes in river flow and wind are included, the model still produces nearly the observed breakup timing even without additional warming. Thus, more than one set of inputs can generate the same timing result.
Determine the transition’s role
The authors are not disputing the timing match or the measured warming. They are limiting what the match can establish about the cause of the shift, so the transition must express that precise qualification.