Besides cognitive learning effects, short-term environmental education (EE) is often regarded as ineffective in intervening with participants' environmental attitudes and behaviour. However, in Germany, school classes often participate in such 1-day EE programmes because they better match the school curriculum in contrast to longer (residential) programmes. We therefore monitored a 1-day outreach EE programme on global climate change to reveal whether environmental attitudes and/or connectedness with nature of tenth graders are affected. Students from German high schools (college preparatory secondary school level, "Gymnasium") (N?=?114) from age 14 to 19 participated in the programme (treatment group). It consisted of two student-centred learning units on the topic of climate change. Additionally, we chose a control group of students who did not participate in the programme. To measure students' environmental attitudes and connectedness with nature, we administered the Two Major Environmental Values (2-MEV) and the Inclusion of Nature in Self scale in a pre-, post- and retention test design. The pre-test was administered 1 week before, the post-test directly after and the retention test 4 to 6 weeks after programme participation. Analyses revealed a positive long-term effect only for utilitarian values (one of the two major environmental factors of 2-MEV) which decreased significantly. Therefore, depending on the programme's content, short-term EE programmes indeed may have an influence on participants' environmental attitudes.