Question

how are climate models developed?

• past data is limited to the 20th century, when we began tracking temperatures and other data points more closely.
• past and present data for various factors, such as co₂ or temperature, are entered into the model to create a baseline.
• they account for both natural and anthropogenic forces within the model.
• models are validated by running data from past years, and if they match it is deemed a good model.
• extreme outliers in the data are excluded to better capture the averages.

Explanation:

To determine the correct options for how climate models are developed, we analyze each statement:

1. "Past data is limited to the 20th century..." – Climate data collection (e.g., temperature, greenhouse gases) extends beyond the 20th century (e.g., paleoclimatic data from ice cores, tree rings). Thus, this is incorrect.
2. "Past and present data for various factors... are entered into the model to create a baseline." – Climate models require historical (past) and current (present) data on factors like CO₂, temperature, and solar radiation to establish a baseline for comparison and prediction. This is correct.
3. "They account for both natural and anthropogenic forces..." – Climate models must include natural forcings (e.g., solar cycles, volcanic eruptions) and anthropogenic (human - caused) forcings (e.g., fossil fuel emissions) to accurately simulate the climate system. This is correct.
4. "Models are validated by running data from past years..." – Model validation involves testing against historical data; if the model’s output matches past observations, it is considered reliable. This is correct.
5. "Extreme outliers in the data are excluded..." – Climate models typically include all data (including outliers) because extreme events (e.g., heatwaves, intense storms) are part of the climate system and must be represented. Excluding outliers would misrepresent the system. Thus, this is incorrect.

Answer:

• Past and present data for various factors, such as $\ce{CO_{2}}$ or temperature, are entered into the model to create a baseline.
• They account for both natural and anthropogenic forces within the model.
• Models are validated by running data from past years, and if they match it is deemed a good model.