What do we know about climate change?
Putting temperature and $CO_2$ in context
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Calculating percentage change
- My weight increased this year from 160 lbs to 170 lbs.
The change in a quantity is just the difference between some initial value and some final value: $$\text{ change}=\text{final amount} - \text{initial amount}.$$
- My weight changed by (170 lbs - 160 lbs)= + 10 lbs.
The positive sign means weight increased.
Often we use the greek letter Delta, $\Delta$, to mean the change in a quantity.
- If $w$ represents my weight, the change in my weight was $\Delta w=10$ lbs.
By what percentage did my weight change? Divide by the initial quantity to get the fractional change, and multiply by 100 to the percentage change: $$\%\text{ change}=\frac{\text{change in a quantity}}{\text{initial quantity}} \times 100\%=\frac{\Delta w}{w_i} \times 100\%$$.
- My weight changed by $(10/160)*100=+6.25\%$.
Sample test question: This summer, the $CO_2$ level measured at Mauna Loa was 416 PPM. That represents what percentage change compared to the pre-industrial level of $CO_2$ of about 280 ppm.
$$\frac{416-280}{280}\times 100 =\frac{136}{280}\times 100 =0.48\times 100 = 48\text{% increase}$$
Temperatures over the last 540 million years
