Googles response from the server is in UTF-8 but some columns maintain their original charset, so your Umlauts or other special charaters will look defect ( e.g. campaignName).

To fix it, you can use TO_CHARS and TO_BYTES.

In Germany these columns are often encoded in windows-1252, so your view can be fixed like in this Example:

create view views.adwords_clicks_per_campaign

AS select

        adwords.customer_id.customerId

        ,campaignId

        ,CAST( TO_CHARS( TO_BYTES( "campaignName", 'windows-1252' ) , 'UTF-8' )  as string ) as "campaignName"

        ,accountId

        ,clicks

    from

        adwords.customer_id

        ,table (

            exec "adwords"."getCAMPAIGN_PERFORMANCE_REPORT" (

                adwords.customer_id.customerId

                ,'2013-01-01'

                ,curdate (

                )

                ,'AccountId,Clicks,campaignId,campaignName'

            )

        ) a;;