In 1980, CO2 concentration in Earth’s atmosphere was 335 ppm.
In 2015, CO2 concentration in Earth’s atmosphere was 405 ppm.
In the last 35 years CO2 concentration in Earth’s atmosphere has increased by (405-335)/335 = 21%.
http://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/co2_data_mlo.png
In 1980, midsummer minimum ice extent in the Arctic Ocean was 7.75 Mkm^2.
In 2015, midsummer minimum ice extent in the Arctic Ocean was 3.75 Mkm^2.
In the last 35 years midsummer minimum Arctic ice extent has decreased by (7.75-4.75)/7.75 =
39%.
http://nsidc.org/arcticseaicenews/files/2015/10/monthly_ice_09_NH 350×270.png
Of course, correllation is not evidence of causation. Maybe the melting ice has caused the CO2 concentration to increase.
Or maybe the rising CO2 levels have nothing to do with the diminishing ice levels. Maybe the correlation is purely coincidental.