causality L3 PQ

1. Why was James ____’s 1988 congressional testimony significant?
c) It ____ future warming ___ that ___ matched later observations

hansen, projected, scenarios, closely

2. Ice core evidence shows that over the last several hundred thousand years:
b) ___ changes generally occurred ___ CO₂ changes

temp, before

3. What caused CO₂ changes in past climate cycles during the Pleistocene?
c) Orbital shifts (___ cycles) triggering temperature changes

milankovitch

4. Which statement accurately describes the modern CO₂ trend?
c) CO₂ rises __ temperature increases

lead

5. Since 1970, atmospheric CO₂ has increased by approximately:

2 ppm/year

6. Which greenhouse gas has a ~100-year lifetime and is the primary driver of long-term warming?

carbon dioxide

8. Which is a major human source of methane?

Cattle agriculture

9. Why do scientists conclude that natural variations cannot explain recent warming?
c) Solar input has barely changed while____ rose rapidly

temperatures

10. Which of the following institutions formally confirmed human-caused climate change in the 1990s?
c) National ___ of major ___ countries

academies, industrial

11. The ___’s main purpose is to:
c) ___ existing scientific ____ about climate change

IPCC, assess, knowledge

12. The 2019 IPCC Special Report concluded that staying below +1.5 °C requires:
c) Cutting global emissions in __ by 2030

half

13. Under current emission trends, global warming of approximately ___ is expected by 2100.

2.7 °C

14. The ice–albedo feedback works because:
b) Ice reflects____ % of incoming solar radiation

50-80

15. Arctic sea ice since the 1980s has:
c) Declined by roughly __

half

16. Which statement correctly describes current cryosphere changes?
c) The ___ ice pack is now about ___ of its past volume

arctic 25%

17. Milankovitch cycles trigger climate shifts primarily by altering:
b) __ radiation distribution

solar

1. Briefly explain why CO₂ acted as a feedback in past climate cycles but is acting as a driver today.

• In past ____*** cycles, ____ shifts changed solar radiation, causing initial ____ changes.

• ___ oceans then ___ CO₂, which ___ warming as a feedback.

Today, human fossil fuel burning rapidly increases ____ first, making CO₂ the ____ of warming rather than a response.

pleistocene, orbital, temperature, warming, released, amplified, CO2, driver

2. Describe two reasons why natural forcings cannot explain observed warming since 1900.

• Solar input has stayed constant or slightly decreased while temperatures rose sharply.

• Natural cycles (Milankovitch) operate over tens of ___ of years, not decades; modern warming is far too rapid.

thousands

4. Explain the significance of James ____’s 1988 testimony.

• Presented early, scientifically grounded ____ for global warming.

• Predicted warming trends with strong vs. weak ____.

• Subsequent temperature rise closely matched his projections, validating early climate ___.

hansen, scenarios, mitigation, models

5. Briefly describe the three working groups of the IPCC.

• WG1 (____): Physical science of climate change.

• WG2 (__, ____, _____): ____ to systems, societies, ecosystems.

WG3 (____): Ways to reduce or ___ greenhouse gas emissions.

science, impacts, adaptation, vulnerability, risks, mitigation, prevent

6. Explain the ice–albedo feedback and why it is especially significant in the Arctic.

• Ice reflects 50–80% of incoming sunlight; when ice melts, ____ surfaces ____ more heat.

• Arctic is warming faster → more melting → more heat absorption → rapid amplification.

• Leads to later freeze-up and ____ ice volume (now ¼ former volume).

darker, absorb, shrinking

7. Identify two major human sources and one major natural source of methane.

• Human: ____ (cows), fossil fuel ___, ___.

Natural: Wetlands.

agriculture, extraction, landfills

8. Summarize two key conclusions of the 2019 IPCC Special Report on 1.5 °C.

• Dangerous ___ likely above +1.5 °C.

• Emissions must fall 50% by 2030; current pathway (+16% by 2030) locks in ~2.7 °C warming.

feedbacks

9. Explain two observed changes in the cryosphere that demonstrate accelerating warming.

• Arctic sea ice has lost ~____% area/thickness; volume now ~____ of historical levels.

• ____ shows more days of surface melt each year, indicating warming.

50, 25, greenland

10. Briefly explain the core mechanism of Milankovitch cycles and their role in triggering ice ages.

• Orbital variations (eccentricity, obliquity, precession) change how solar radiation is distributed across Earth.

• Reduced summer ____ at high latitudes allows ice sheets to ___ → ____ periods.

• Increased sunlight reverses this → ____ periods.

sunlight, grow, glacial, interglacial