The graph shows satellite measurements of global sea level rise since 2000 plotted relative to 1993. (sea level rise measured in mm = millimetres)
a) Draw a line of best fit through the data and write an equation for your line in the form y = mx + c, to show how sea level is rising through time.
[3 marks]
b) What are the units of your value for mx, and c?
[1 mark]
c) Using your equation, work out how much higher sea level will be in 50 and 100 years’ time.
[2 marks]

Some scientists think that sea level isn’t rising with a constant rate, but is in fact accelerating.
Fitting a quadratic curve to this data gives the equation, y = 0.05x 2 + 2.6x + 21.3.
d) What are the units of the value for 0.05x2?
[1 mark]
e) Use this equation to calculate how high sea level will be in 50 and 100 years’ time.
[2 marks]
f) What is the difference between your answers in (c) and (e)?
[1 mark]