Impax Environmental Markets posted a positive performance in the first half that beat its benchmark.
The investment company -- which targets markets for cleaner or more efficient delivery of basic services of energy, water and waste -- posted a net asset value total return per share of 25% for the six months through June.
The FTSE ET 100 Index rose 16.0% over the same time period.
'We expect market conditions to remain volatile over the months to come,' chairman John Scott said.
'Growth is slowing, with the global economy facing challenges on a number of fronts.'
'Foremost among these are continuing US-China trade tensions, the unravelling of the Iran nuclear deal, with possible implications for the oil price, and the risk posed by a disorderly Brexit to the UK and EU-27 economies.'
'As the second half of 2018 showed, the company's performance can be vulnerable to factors with little direct bearing on the environmental markets theme.'
'IEM has a high tracking error -the difference between its performance and that of its benchmark - meaning that, in volatile markets, it may temporarily under- or out-perform by a significant margin.'
'We are confident that, over longer periods, it will deliver attractive returns for investors and we note the company's excellent long-term record.'
'The board retains its conviction that growing resource constraints in the context of global population growth and rising public concern over environmental degradation will continue to underpin the company's investment thesis.'
At 2:55pm: (LON:IEM) Impax Environmental Markets Plc share price was +1p at 311p