Eight years ago we built an online dialog capability to supplement student class-time discussion of course topics in a senior undergraduate/graduate course in Global Change. We naively thought this would promote deeper learning. The resulting discussion could most accurately be described as superficial remarks, spiced with personal agendas, religious fervor, cutesy comments, and an occasional spark of academic interest. We quickly realized we needed a different means of explicitly emphasizing use of critical thinking skills and social interaction to enhance learning. In the current implementation, students are required to submit 21 online writing assignments during the semester as part of the online threaded dialog on global change issues. Fifteen of the 21 postings must individually demonstrate one or more of the defined critical thinking skills (CTS): (analysis, synthesis, organization, articulation, brainstorming). Students declare in advance of the posting the type of CTS to be used. In the follow-up self assessments submitted at five-week intervals they defend their choices of CTS categories. Social interaction is promoted through requirements for responding to nine other student postings and receiving response postings from nine other students during the semester. Forty-two three-question multiple-choice quizzes are taken online by each student during the semester (one for each of the learning units covered in the course) that also require one or more CTS to determine correct answers. A comment box provides opportunities to explain reasoning or argue that the correct answer is not given as a choice. An electronic portfolio system with versions for students and instructors has been developed to manage online threaded dialog; links to course materials; quiz scheduling and scoring; public, private, and group dialog; and dialog statistics. Online availability of all students’ products, self assessments and instructor evaluations is a powerful tool in confronting student weaknesses. It more resembles a face-to-face encounter with all evidence laid out than a piecemeal return (and often immediate disposal) of paper-based written materials over the course of the semester. The major challenge in implementing such a system is the demand on instructor time, and the major challenge to our further development of the online portfolio is how to ease that burden. Results of implementation over the last 3 years will be described.