The line chart illustrates 
average
 Co2 footprint per individual in four countries including the Correct article usage
the average
UK
, Sweden, Italy, and Portugal over 40 years. 
Use synonyms
Overall
, Linking Words
it is clear that
 the Linking Words
Uk
 Use synonyms
aand
 Sweden showed Correct your spelling
and
declined
 in Replace the word
decline
Use synonyms
amount
 of Co2 Add an article
the amount
emissions
 during Use synonyms
given
 period , Correct article usage
the given
while
 Italy and Portugal showed Linking Words
Correct article usage
an increased
increased
. Replace the word
increase
Furthermore
, the highest country in Linking Words
Use synonyms
amount
 of Add an article
the amount
green house
 gas was the Correct your spelling
greenhouse
UK
, Use synonyms
whereas
 Linking Words
lowest
 country was Portugal.
Looking at Correct article usage
the lowest
chart
 in more detail, from 1967 to 2007 the Add an article
the chart
Uk
 was the highest Use synonyms
amount
 of carbon dioxide (Co2) Use synonyms
emissions
  from approximately 11 to 9. Use synonyms
In contrast
, Portugal was the lowest Linking Words
amount
 of Co2 Use synonyms
emissions
 almost from 1 to 5.5.
Regarding other countries, Sweden reached a peak of Use synonyms
Use synonyms
amount
 of Co2 Add an article
the amount
emissions
 Use synonyms
at
 1997 around 10.2 and Change preposition
in
then
 showed Linking Words
decreased  
to almost 5.6 in 2017. In comparison, from 1997 to 2007  Italy was the second country Replace the word
decrease 
release
 Co2 Fix the infinitive
to release
emissions
 from approximately 6.2 to 7.8.Use synonyms