When Malaysian solar company Tadau Energy issued the first ever green sukuk in 2017, it was an important moment for green bonds, as the phrase entered the lexicon of Islamic financing.

Oslo-based external reviewer Cicero's 'dark green' second opinion on Tadau's framework was in many ways just as important, in that it helped define a level of 'greenness' for Islamic investors, and opened 'a new frontier' for clean energy investments, Cicero said.

Proceeds from the MYR250 million ($59 million) transaction were to support solar development in Malaysia, a technology which is key to a low-carbon transition.

Unlike other second-party opinion providers, Cicero classifies the strength of an issuer's green bond framework on a 'shades of green' scale ranging from light green (least contribution to the transition to a low-carbon economy) to dark green (highest contribution).

This first green sukuk – a bond that adheres to Sharia rules – paved the way for others, including the first sovereign green sukuk, issued by Indonesia in February 2018.

In winning the award, Cicero, whose opinions were used on some $23 billion of issues in 2017*, beat off stiff competition from other second party opinion providers, such as Sustainalytics, and other forms of assessments, such as from ratings agencies, S&P and Moody's.

A judge on the awards selection panel praised the academics at Cicero - which stands for Centre for International Climate and Environmental Research in Oslo – for providing "real thought leadership", and for "not just completing the job, but developing the discipline".

Another example of Cicero's work was its assessment of the green bond framework of Industrial and Commercial Bank of China (ICBC) – the world's largest commercial bank – providing a 'dark green' assessment and praising it for 'impressive impact reporting'.

The framework set an example for international transparency for Chinese green bond issuers, the external reviewer said. Cicero praised the framework for its "impressive" commitment to impact reporting, and noted favourably that ICBC will engage an independent third party to provide assurance on its annual green bond report.

The bank's subsequent, three-tranche, multi-currency green bond, which was issued in October, had a combined value of about $2.1 billion, with maturity dates between 2020 and 2022.

*Figures according to Environmental Finance's Green Bond Database