Climate Science and Climatology Flashcards

Atmospheric CO2 concentrations have surpassed approximately what level in recent years (mid-2020s)?

Answer: 420 ppm

Atmospheric CO2 concentration has exceeded 420 ppm in the 2020s, compared to the pre-industrial level of approximately 280 ppm, representing a ~50% increase driven by fossil fuel combustion and land-use change.

Which climate feedback amplifies warming by reducing the extent of highly reflective surfaces at high latitudes?

Answer: Ice-albedo feedback

As temperatures rise, ice and snow melt, exposing darker ocean and land surfaces with lower albedo, which absorb more solar radiation and further amplify the initial warming in a positive feedback loop.

The Planck feedback in the climate system is classified as:

Answer: A fundamental negative feedback that stabilizes climate

The Planck (blackbody) feedback is a stabilizing negative feedback: as surface temperature increases, the planet emits more longwave radiation to space, acting as a restoring force against further warming.

Equilibrium Climate Sensitivity (ECS) is defined as the equilibrium global mean surface temperature change resulting from:

Answer: A doubling of atmospheric CO2 concentration

ECS is the long-term global mean surface temperature increase after the climate system reaches a new equilibrium following a doubling of atmospheric CO2, with the IPCC AR6 likely range of 2.5–4.0°C.

The current rise in global mean sea level is primarily attributed to:

Answer: Thermal expansion of seawater and mass loss from glaciers and ice sheets

Current sea level rise is driven roughly equally by thermal expansion of warming ocean water and by mass contributions from melting mountain glaciers and the Greenland and Antarctic ice sheets.

IPCC Shared Socioeconomic Pathways (SSPs) are used in climate projections to represent:

Answer: Different assumptions about future greenhouse gas emissions and societal development trajectories

SSPs describe plausible alternative futures combining different mitigation challenges and socioeconomic conditions, ranging from SSP1-1.9 (very low emissions) to SSP5-8.5 (very high emissions) to bracket the range of possible futures.

The 'hockey stick' reconstruction of Northern Hemisphere temperatures, first published by Mann et al. (1999), is significant because it illustrates:

Answer: Relatively stable medieval temperatures followed by rapid warming in the 20th century unlike anything in the past millennium

The reconstruction showed a relatively flat shaft of roughly stable temperatures over the past ~900 years followed by a sharp 20th-century upturn (the blade), demonstrating that recent warming is unprecedented in at least 1,000 years.