The graph shows NOAA global atmospheric CO₂ concentrations. What does the record show?

The graph shows annual atmospheric CO₂ measured at Mauna Loa. About how much did concentration increase from 1960 to 2020?

The graph shows global surface-temperature anomaly relative to a long-term average. Which interpretation fits the full record?

The graph shows NASA global surface-temperature anomaly. What was the 2024 anomaly closest to?

The graph shows Arctic September sea-ice extent from satellite observations. What is the long-term pattern?

The graph shows satellite-measured global mean sea-level change since 1993. Which estimate is supported for the change by 2020?

The graph shows Mauna Loa annual CO₂ values. Which displayed decade had the largest increase?

The graph shows global temperature anomaly. By about how much did the anomaly increase from 2000 to 2024?

Air bubbles trapped in an ice core are analyzed layer by layer. What do the bubbles preserve?

At a moisture-limited forest site, wider tree rings form in wetter growing seasons. What can an interval of unusually narrow rings indicate?

Scientists analyze oxygen isotopes and trace metals in a coral skeleton. What past condition can these measurements help reconstruct?

A sediment core from a lake contains pollen grains in successive layers. What can the pollen record directly identify?

Why do scientists use proxy records such as ice cores and tree rings to study ancient climate?

An ice-core layer contains a sharp spike in sulfate along with fine ash particles. What past event does this layer most directly support?

A proxy reconstruction overlaps an instrumental temperature record for 80 years. Why is the overlap useful?

Which observation is proxy data rather than a direct instrumental climate measurement?

What makes ice cores especially useful for reconstructing climate over long time scales?

A glacier's long-term mass-balance record shows more ice loss than gain in most years. What does this physical record indicate?

What two warming-related processes are primary causes of global sea-level rise?

As atmospheric CO₂ rises, more CO₂ dissolves in seawater. Which chemical change is expected?

Ocean heat-content measurements rise over decades. Why is this an important climate indicator?

For several decades, a plant population flowers earlier in spring at the same site. What biological climate signal does this most likely show?

A mountain region warms steadily over many decades. Which range change in a cold-adapted mountain species is most consistent with this warming?

Bird records show that spring migration begins earlier over many decades. What type of evidence is this?

A town has its coldest January in 30 years while global records show multi-decade warming. What conclusion fits both observations?

A strong El Niño contributes to an unusually warm global year. What does that single year establish about the climate trend?

The graph shows annual global temperature anomalies. What does the drop after 2016 demonstrate?

The graph shows Arctic September sea-ice extent. What does the increase from 2020 to 2023 show?

After a major volcanic eruption, reflective aerosols temporarily cool the climate. How should this effect be interpreted in a temperature record?

What evidence most reliably identifies a climate trend rather than short-term weather?