Read the passage and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
Earth’s climate has never been a static backdrop to human history; rather, it has oscillated continuously under the influence of forces both celestial and terrestrial. Long before industrial smokestacks pierced the skyline, temperatures rose and fell in measured cycles, paced largely by variations in Earth’s orbit and axial tilt. [I] These subtle astronomical shifts, unfolding over tens of thousands of years, regulated the advance and retreat of ice sheets and governed the rhythm of glacial and interglacial periods. Crucially, even at their most extreme, such natural fluctuations remained confined within relatively narrow thermal boundaries.
In popular discourse, the Sun is frequently portrayed as the prime suspect behind contemporary warming. Yet this narrative collapses under scrutiny. Satellite measurements spanning several decades reveal that solar output follows predictable cycles without exhibiting a sustained upward trend.
Meanwhile, global average temperatures continue their steady ascent. The implication is difficult to ignore: although solar energy establishes the baseline conditions for life on Earth, it cannot account for the rapid and persistent warming observed in the modern era. [II] The Sun, it seems, has become a convenient distraction rather than a credible explanation.
Equally influential is the planet's surface itself, which determines how incoming energy is absorbed or reflected. Ice and snow, with their high reflectivity, deflect a significant portion of sunlight back into space. As these surfaces diminish, darker land and ocean areas absorb more heat, intensifying warming through a self-reinforcing feedback loop. Volcanic eruptions occasionally interrupt this process by injecting aerosols into the atmosphere, temporarily dimming sunlight and cooling the planet. However, such episodes are fleeting, their climatic fingerprints fading within a few years. [III] They are interruptions, not drivers, of long-term change.
Carbon dioxide occupies a more complex position in Earth’s climatic history. Ice core records show that its concentration has risen and fallen in tandem with temperature, often amplifying changes initiated by orbital shifts. In the past, carbon responded; today, it leads. Human activities—chiefly fossil fuel combustion and deforestation—have propelled atmospheric carbon dioxide levels far beyond their natural range, and at a pace unmatched in geological records. [IV] This abrupt forcing has tilted the climate system away from its historical equilibrium, underscoring a critical distinction: while climate change itself is ancient, the current trajectory is both anomalous and overwhelmingly anthropogenic.