What evidence shows a correlation between global temperatures and carbon dioxide concentrations on Earth?

The correlation between global temperatures and carbon dioxide (CO₂) concentrations is supported by various lines of evidence, particularly from paleoclimate data, modern observations, and climate modeling. Here are the key points illustrating this relationship:

1. Paleoclimate Evidence

• Ice Core Data: Studies of ice cores from locations such as Vostok and Dome C in Antarctica have revealed a strong correlation between CO₂ levels and temperature over the past 800,000 years. As CO₂ concentrations increase, global temperatures also rise, and vice versa. This relationship is evident during glacial and interglacial cycles, where changes in CO₂ levels closely follow temperature changes, demonstrating a feedback mechanism between the two.
• Hansen’s Graph: Research has shown that historical data from ice cores indicates a significant forward and reverse correlation between atmospheric temperature and CO₂ levels. This correlation is not only observed in Antarctic cores but also in other locations, confirming that higher CO₂ concentrations are associated with warmer periods.

2. Modern Observations

• Recent Trends: Since the Industrial Revolution, atmospheric CO₂ levels have risen sharply due to human activities, leading to an increase in global temperatures. NASA reports that the average surface temperature has increased by approximately 1.36°C since the late 19th century, coinciding with a rise in atmospheric CO₂ from about 280 ppm to over 415 ppm.
• Statistical Correlation: Modern studies employing statistical methods have established a strong linear correlation between CO₂ concentrations and global temperatures. For instance, one study found a correlation coefficient (R²) of approximately 0.9216 when analyzing temperature changes against CO₂ levels since 1959.

3. Causal Relationships

• One-Way Causality: Research has indicated a one-way causal relationship where increases in CO₂ lead to rising temperatures rather than the reverse. This conclusion is supported by various studies showing that while temperature changes can influence CO₂ levels over long timescales (such as during glacial cycles), recent trends demonstrate that current warming is primarily driven by anthropogenic CO₂ emissions.
• Climate Models: Climate models consistently predict that rising greenhouse gas concentrations will lead to increased global temperatures. These models incorporate historical data and project future warming scenarios based on different emissions pathways .

4. Feedback Mechanisms

• Temperature and Carbon Release: Warmer temperatures can lead to additional carbon release from natural sources such as soils and oceans, further enhancing the greenhouse effect. This feedback loop indicates that as CO₂ levels rise and temperatures increase, additional mechanisms can exacerbate warming