The graph cannot answer questions about the slope of the line of best fit or provide information about sea ice extent in the southern hemisphere. It can be used to observe the data variability and compare it between earlier and later years.
1. To determine the slope of the line of best fit, you need the coordinates of two points on the line. Unfortunately, the graph and the question do not provide the specific coordinates needed to calculate the slope of the line.
2. The graph only shows data for the Arctic region, not the southern hemisphere. Therefore, it cannot tell us anything about sea ice extent in the southern hemisphere or compare it to the results from the article.
3. The variability of the data can be observed by looking at how spread out the data points are on the graph. By comparing the range of data points between earlier years and later years, you can determine if the variability has increased or decreased.
4. The graph and the question do not provide any information or context to suggest possible reasons for the changing variability in sea ice extent between 1980 and 2018.